Hi! I immediately related to your symptoms because it's exactly what I experienced in my 2002 NB (now at 102 000 km). Jerking/stalling especially under load and heat (30°C +, highway speed 110-115 km/h, then traffic slowdown). Engine would die and restart normally after those events. So I went to visually check my crankshaft position sensor (1.8 L engine). Found the plastic bracket was cracked and the gap with the pulley seems way too big! Ordering the CAS today, pretty confident it will solve this nasty problem. By the way I also had no code after those events. Thanks a lot for pointing me in the good direction! Finally after closer inspection the CAS gap with the pulley metal tab was within specs (.032"). And the cracked bracket was still holding the sensor tight. I went to replace it anyway convinced it was deffective and sensitive to heat. But same problem showed up on test ride.
@@Adventureswithhim Hi Dan! Replacing the Camshaft Position Sensor did fix the problem. I did my best to make it failed but the problem did not reappeared (engine stumbling, stalling and re-starting after few minutes). You have to drive it hard in hot conditions (>30°C) to prove it good. I don't expect this trouble to comme back next summer! Make sure you buy the newer version of this sensor, there are cheaper version on the market but they are the old type.
It is BOTH a cam position sensor AND a CRANKSHAFT position sensor. It is driven by the camshaft, but if it only had the cam signal, it wouldn't know where the piston was. The Miata CAS has two rows of circles cut into a disc. The outer row has 4 symmetrical slots and this is the spark signal for the four cylinders. The inner row has two holes or slots, one being 3 times larger than the other. This gives it a dot - dash sort of signal. The two inputs together tell the ecu relative piston position and which cylinder to fire. Some CAS are Hall Affect sensors and some are optical with diodes. Both have a shutter type system. BTW, our Mazda Miata CAS is made by Mitsubishi.
@@WrongwayPilot My miata would stutter on the highway and get progressively worse the longer I drove until it would essentially die. I ended up replacing the air flow meter, coil pack, throttle position sensor (tps), the CAS, and both temperature sensors (one in the front and one in the back) to try to find the issue. Turns out the CAS was leaking oil on the temperature sensor behind the engine and causing all my issues. Definitely look at the temperature sensors if you get a chance. They are relatively cheap and quick fix.
@@jonahharrington7398 Thank you for the advise- funny enough my temp gauge hasn't been sitting in it's normal halfway spot, recently since I have had this issue its been sitting about 30%
@@jonahharrington7398 Hey man thought I would give an update, turns out it was alternator playing up was only charging at 13v instead of 16v so new alternator and the issues are gone atm hopefully they wont come back, haven't been on the highway yet though that will be Monday
Hope this is my problem. 89 NA Eunos. Changed the fuel pump, filter, spark plugs, plug leads, o2 sensor, drained all the fuel (thought maybe I had bad fuel as I just topped up) and no luck. This CAS sensor will be arriving tomorrow so will see if it’s any better!!
Thanks! Is the o ring leaking what causes the issue? I have the new circuit board for the sensor and a o ring.. would rather replace the o ring than the internals of the sensor
It can be. If you can clean it out and it works, then an oring might be enough. If not, the board is probably bad. It could also be worn out elsewhere.
I’m thinking I may be having CAS issues aswell. On long highway stints like 1-2hrs my 91 would stumble and cut out and eventually completely die. Soon as I restart the engine it’s perfectly fine again.
@@AmbiVe it’s a Eunos roadster I bought it about 11hrs away from home so CAS issues on top of learning to drive RHD made it an intersection drive home 😂
I've been having a similar issue with my VVT swapped 91. It'd stumble at both idle and load. Since I'm running a Megasquirt ECU, there was a "sync loss 31" in the data log, which points to the cam sensor. Apparently they're prone to failure on the NB's, but from doing some research, Mazda has updated the design in recent years, so the failures aren't nearly as common.
I got a question I have a 91 NA Miata first it started jerking or stumbling when I was on highway once I kept a steady speed or once I hit certain rpms. thought their was water in fuel checked that got fuel assembly and all that replaced so it should be good. The next day went to start it left it outside for maybe 7/8 min running then I cam out and it had cut off. tried starting again it would crank over but no start
That could be ignition, this Miata got worse after running and getting warm. It could be the coil, ignition chip, or CAS. My bet would be CAS, but that's a guess without troubleshooting each part.
I used to have these exact symptoms, and eventual failure, on my 1991 v6 3.0 4Runner. It turns out that it was the Ignitor. The Ignitor & the coil are both connected by the same bracket. It was an ongoing problem for about 2 years till it completely failed & would no longer start. Oh & by the way, I do have a 1990 Miata, 1.6 that is ready for the paint job, & I'm currently waiting for the machine shop to call me, to pick up my engine block & cylinder head for me to assemble & reinstall on my miata. Anyways, while on the freeway, the same thing would happen to me as with your gal's Miata, suddenly a violent quick stall that would just as fast would reignite the engine. This was usually at 65mph or higher, so obviously mostly on the freeway. And just like your Miata, the high speed at which this would happen, would have momentum enough to quickly reignite the engine. And since my 4Runner is stickshift, it was like push-starting the vehicle but at freeway speeds. Once it left me stranded, my friend & I immediately knew it was the igniter. I ran the pre-OBD2 self diagnostics, & sure enough, it gave a code for the ignitor. I couldn't find the extra OEM ignitor that I jacked from the junkyard, so I bought one from Oreilly's. Turned on right away. I got to point out something else, a part that is similar to the Miata & the 2nd generation 4Runners. That's the AFM, Air Flow Meter, which is frequently confused with the MAF, Mas Air Flow sensor. Both serve the same purpose but the MAF was or is the newer version of the AFM, as I understand it. When this MAF starts giving problems, it can be confused with the CAS problems because they are intermitten problems...once in a while, till it gets worse, then leave you stranded. It will also have you chasing your tail...changing fuel pump, relays, fuel dampners, etc. till it fully fails & leaves you stranded. Good thing is that here in Southern California we have an abundance of junked cars, dry, not rusted nor ruined from salted snowed-in roads. Unfortunately since these same generation cars have parts that are as old as yours, the life expectancy is similar & soon enough I found myself trading in my junkyard replacement for a NAPA remanufactures AFM, which is still good today. If i ever go through these same problems on my miata, at least I know the likely culprit of the problem.
I believe this may have helped solve my problem. I'll look into getting a new CAS, so thank you very much. Quick question just to verify, though. My NA has been doing the aforementioned things, and it has progressively gotten worse to the point of it not starting anymore. If I jump the battery, the engine stays on only if I continuously rev. As soon as I stop, it dies again. Does this sound like a bad CAS to you?
@@RoxusRemo yes, turns out it was the alternator bracket working itself loose and not putting enough tension on the belt! Got a new belt since the old one glazed pretty badly and it’s been running great ever since! Good luck
Interesting. I wonder what it is that fails inside the CAS? I have an NA6 also. And I am replacing the catalytic converter every few few years, so the car has been running rich. If there have been misfires, that would explain a lot of unburned fuel in the exhaust that is killing the cats. Now that catalytic converters are quite expensive, this does not work well as a temporary solution.
That could certainly kill cats. The CAS doesn't always fail predictably, so it could continuously be varying the misfires and burn enough that it damages the cats but runs well enough to get by.
@@AmbiVe apparently the CAS sensor in the NA6 (89 thru 83) versions of the car is an optical switch. The NA8 and later are said to be Hall effect sensors. They are pretty simple devices. There are four pins. Pin 1 is Ground. Pin 2 gets 12V. Pin 3 pulses 4 times per cam shaft turn. And Pin 4 pulses long 1 time then short 1 time per cam shaft turn. LEDs do lose brightness over time. I can imagine this producing an irregular signal, that trips the photo diode receiver most of the time, but not all of the time.
Okay. I just gave in and bought one. The NA6 has old school optical sensors. After 30 years it doesn't owe me anything.. Modern replacements have Hall effect sensors. Prices on these are all over the map. I bought a Walker for $175.
I know I’m a bit behind but would it make sense for a bad cas to cause a wierd tach reading sometimes? Like sometimes it will be normal then sometimes it will be 2k rpm off and kinda lazy
I haven't seen the tach read strangely just because of a CAS. That sounds like other electrical issues, especially if it's just the tach reading and the engine isn't actually jumping around RPM. I believe that wire comes right out of the ignitor.
my 99 miata did this a couple years ago (died while driving on highway, somewhat spirited rpms) i replaced fuel pump and coil) just a couple weeks ago it died while driving on highway with ac on. would not start. waited 15-20 minutes and it started and made it home fine, no issues, about 15 miles. Any suggestions? ty
I'm having the same issue but the only difference is that it does not sputter and there are no rough idling, it happens super seldom and only when coasting in neutral. I'm caught by surprise that the engine is already dead as there are no signs that it has died, no violent shaking etc. Any idea on what this might be? Just replaced the AFM but still the same.
I bought a Miata from someone a couple months ago. It sat in their garage for a year, and when I got it it had bad gas, and I had to change the fuel pump. Changed it and it worked great. I let it sit again for a while because I had other stuff to work on and now I barely got it to crank And sometimes turn over. The first couple of times when I try to start it , it starts and runs decent, Then stauls. After trying to start it and keep it running it’ll die faster and faster everytime. It’ll idle less and less every time for a couple seconds. Then won’t start and idle at all. Any one having this issue?
If it will barely crank then it sounds like an electrical issue or engine mechanical issue. Is your battery good and all connections solid? You might have several issues ranging from electrical to plugged fuel filter or injection system. Start working through each individually. Get your volt meter and check the voltage through the system and of the battery. After you know you have solid voltages and a good battery, then move to the fuel issues that might result in it dying. If the fuel system is good, then move to ignition. Sitting is hard on cars. Good luck!
Hit the mark for me. Got engine rebuilt and code now shows up and have all the symptoms. Uneven acceleration, stumbling, hesitation, j can j feel it basically and it all makes sense now😄
A lot of these symptoms are what my 95 Miata is experiencing right now. The car would run and drive fine, but when I would put it in neutral and coast, the RPM's would drop very low and sometimes stall. This wasn't a super bad issue until just a few days ago when I was starting it to go to class, it started, proceeded to shutter and die and now I can't get it started. I am assuming its the CAS, any ideas?
I had an issue about a year an half ago with my 2001 NB MX5 where i would drive but then it started to jolt and stall, I replaced CAS didnt fix it, i replaced the fuel pump and it fixed it. BUT now im having a similar problem, i drove the car and it would jolt and stall, so i parked it in my driveway, now it wont even start, sometimes it successfully starts but then dies immediately, i replaced spark plugs, coil packs and leads still didnt fix it. All the issues seem to be CAS But how would the CAS Fail after a bought i genuine one a year and half ago..
If it's slow to turn over, it's probably more likely a battery or starter issue. If it turns over without issue and is getting fuel, then it could be CAS related.
Hi thr, my 1.6 na idles good but sometimeees the rpms reaches low as 250/300 rpms, over 3000/3500 usually starts running poorly and looks like is not going anywhere, i suppose is cause a bad cas bt here in europe (in italy precisely) i cannot find anything undr 600/650 dollars, i really neet it to be replaced if it is the problem, can i import it from us or something else?
If it's just idling erratically or too high and too low, I wouldn't start with the CAS. I would check for error codes in the computer and vacuum leaks. Then maybe look at the idle control system.
That could be a weird CAS issue. It could also be a load sensor issue, like with the air flow sensor or in the ignition system. If the load isn't being reflected properly, the engine will try to run as if the throttle is totally open or closed when it's not, tricking the fuel system into freaking out and then correcting when the o2 sensor gives the computer feedback that it's way too rich or lean.
One of the bad CAD symptoms we had was that the car would be running great and then just die while cruising down the road and fail to start again until it cooled down. So it could be. Bad CAS do weird things on NAs.
Quick question I have a 2006 Mazda Miata and it dies while driving, I’ve replace gas pump, the switch at the end of the key switch but still dies. I clean the throttle body too. Is automatic though does my car have that part you replace in your girlfriend’s car?
I'm not sure how the 06 is setup, but they will all have some system for ignition timing vs cam or crank position. You could look up your specific car to see how it works for sure. That does sound like a spark issue or fuel, and since checked fuel pump, my guess is either the computer, fuel pump relay, or ignition system side. Good luck!
I’m not entirely sure if we’re having the same issue too, we just got a 93 auto for my gf and noticed a pretty aggressive jerk what seems to be around 2nd gear that it shifts too but then 3rd and 4th smooths out. Would that be a cause?
If it's an automatic and it only happens during a single gear change, it's probably a transmission issue. Miatas were never meant to be automatic, so maybe the car gods are offended? It could also be the transmission having a clutch or pressure issue.
I am having a problem when on coils 1 it will only fire once every few seconds and on coil 3 it won't even fire at all. I a new coil pack in and the same problem is accuring. Could this be the cas or would it be a crank position sensor. Any help would be very nice
I would say that it could be the CAS or possibly another portion of the ignition system or control. These CAS are so flaky, especially the Chinese reproduction versions, that it's a solid guess to start with.
@@AmbiVe I was looking around the engine and I noticed that the crank position sensor wire was ate through a little bit by the belt. The car will start up perfect and idle but as it warms up the idle will start to surge up and down. I wonder if that is the problem
My NB has these symptoms, though it does not immediately re-start. Takes minimum 15 minutes. One garage said fuel - replaced fuel filter ("full of rust")....but still had the problem.
I actually just came across this video and I have been having a no spark issue with my 90 Miata for a while now but i did have a question. If the CAS is bad will it still have power up to the coils but it wont have spark? I bought this car with 2 coil packs and i kind of doubt both of them would be bad so I'm just seeing how this system works before I buy a new CAS all together.
Not just doing the CAS. It is keyed to only connect one way. It is simply a pain to figure out which way that is when you're upsidedown and backwards in the engine bay ;)
Just did the timing on my 90 1.6 and at idle it stumbles/Missfires, I’ve looked at everything I can think of and I have no clue what it could be, it also has an exhaust pinging when you apply 1/4 throttle or more
Hi Casper. In your opinion, how much better or what's the difference between a car that has a CTS and a car that does not need one? In other words, why does a car need a CTS?
The CAS/CTS/etc, essentially replaces a distributor that you would see in an older car. In say my Mustang, the rotation of the engine rotates the distributor which triggers a spark each time the rotor completes a circuit at each plug wire on the cap. In essence, a CAS effects the same thing, but via either triggering an individual coil per plug or through another system with control of the coils, disconnected from the actual carrying of the high voltage. Both systems are just there to allow the system to initiate a spark at the correct time for the position of a given cylinder. I would say that a CAS/CTS is a better option overall as you have to have something filling that role to have sequential injection systems accurately in a better package. Now, if having it read a cam shaft vs a crank pully vs the oil pump shaft has a pro or con, I don't know. The SR20DET in my Z pulls it from the cam as well for it's CAS, but a lot of aftermarket systems just use magnets on the crank pulley externally to make them platform independent. Edit: This is assuming you were talking about crank timing sensors and not coolant temperature sensors. That would be a while different can of worms 🤣
I have the same problems but it tachs then it would die. When at times I give it throttle multiple times and it would start again.I’ve changed all my grounds
I have a 1992 Miata with a 1.8 engine swap and basically whole drivetrain from a 1994 model. I had a similar issue, was driving and hit a rather bumpy patch of the road and immediately after the tach dropped to zero and it felt like the whole engine turned off while I was still doing about 40 miles an hour. The engine turned back on in like a split second. But after that incident it did it 4 more times on the way home and every incident got a little bit worse and sketchier. When I pulled in my driveway the car was idling fine but the fuel pump was making a weird noise. Almost sounds like a washing machine running in the distance if that makes sense. Does this sound like a CAS issue to y’all? Any recommendations? Thanks for any input I really appreciate it.
It sounds like you have something loose. Since it died and runs so rough, I would check that the CAS didn't move and mess up timing, that all your ignition connectors are right, your coils are tight, and your grounds are all clean and tight.
My NA was running a little hot, but mostly fine... Suddenly died at low rpm while *descending* a hill... Couldn't get it to start again. Cranks hard but no juice. Faulty CAS?
NEED HELP! My 96 1.8 has 179k miles! She ran great and is my daily!!! Driving to windy roads the other day when she just shut off on the highway, fuel cut and looked in the bay to see for any blown fuses or unplugged plugs!! Never left me stranded so knew it must’ve been something stupid! Get it towed to my mechanic and his diag was the CAS! P0335 code! I went and got one from a friend and still isn’t working! My mechanic says it’s now not getting spark! I found another CAS that I’m just going to buy to the hell of it for $50! I’m so annoyed! I love this car and it’s my daily! Start school Wednesday and desperate to diag and fix her! Please help me!!! I’m a junior mechanic but id rather it be looked at by a master mechanic etc…thanks!!
If you don't have spark it could be CAS, ignition chip, or coil. Each one has a specific testing process that generally just requires a multimeter and some time. Either take some time to test or open the wallet and throw parts at it. The CAS is the most expensive part, so if your friends was good, it shouldn't be as bad if it's the chip or coil.
Hi! To solve the problem descibed in my previous comment, I went to Mazda and bought a brand new CAS (BP4W-18-221B) which is identical to the one I removed. Installed it today and went for a test ride trying to duplicate previous failure conditions: external temp 30°C +, sustained highway speed preceeding a long traffic slowdown. Sure enough I had the exact same failure as before and needed to stop on the side! I was very surprised as I really suspected the CAS to be the problem. In your case, at the end and after changing a lots of parts, what exactly made you think that the CAS was at fault? Is it possible that my two identical CAS behave exactly same in heat condition? Thanks for helping me on this issue!
I received a bum CAS in the past and had to replace it again shortly after testing. It's also possible your ignition chip or coil could be having heat issues. It's hard to pin these vague issues down unfortunately.
Ok, I just went to check if I had any code recorded (I had none with the previous sensor). But now I have one: P0340 - Camshaft Position Sensor A Circuit Bank 1 or Single Sensor.
Hi again! Just to up-date on my 1.8L engine stumbling and stalling at hight load and temp. Because it is different from earlier 1.6L engine, in my trouble-shooting I mistakenly confused between the CAMSHAFT and the CRANKSHAFT POSITION SENSORS! Replacing the CRANKSHAFT position sensor did no good (and the old part was identical to the new). Realizing my mistake I ordered and replaced the CAMSHAFT position sensor (now this part is different from the original. Same Mazda part number but different Mitsubishi p/n engraved on the part!). I them went on a road test trying to duplicate the conditions (not easy!) which triggers a stumbling/stalling fault. It passed the test with no problem with the engine and no fault code locked on the tester. I leave just a tiny doubt for the future but I am now pretty confident that the CAMSHAFT position sensor was the real culprit! Thanks for your help!
My N/A Miata is having all the same symptoms you said but it jitters when I stay cruising at 4k rpm and then when I mash the throttle to do a pull the engine completely dies and if I hold it down it fully dies and turns off
I have cylinder 3 and 4 not having spark at all. Because whenever I pull it while the car is running. The car wouldn’t shut off.(I did this test maybe twice?) I changed ignition coil, spark plugs and spark plug wire still doing the same thing. I just changed the injectors as well. Literally just 3 and 4 is misfiring. Maybe a bad CAS? I remember when I tried to change the O RING and I cleaned the cas with tons of Break Parts Cleaner and idk if that’s the cause of MAYBE the cas being broken.
If it's only specific cylinders, I would try swapping around plug wires and plugs. If it doesn't change, I might try another coil or jump to assuming that the CAS or ECU might be having issues. Cleaning it could have caused an issue, but if you looked at cleaning it in the first place, it may have been bad all along.
I have a 1990 Miata and when you give it gas it dies , I’ve replaced a ton. I actually put a new cas on the car a few months ago but I’m curious if maybe it had went out in a few months after being replaced
Hey man I’m having issues with my 91 NA as well. The car will start but after driving when the car is shut off the car won’t turn on again it’ll crank but no start. Sometimes it’ll start for 2-3 seconds and stall out but after waiting like 10 to 15 minutes it’ll start right up… but again if it’s turned off it’ll crank and won’t start again I have no clue if it’s my CAS or crank position any help? Thank you!
@@AmbiVe is there any way to check it? Like with a digital multimeter or? Becaus the cas isn’t cheap per say haha I wouldn’t want to spend the money of that isn’t the issue
There are a few ways, however, none of them worked for the sad CAS on our Miata. I think it would work of the CAS was totally dead, but if the car starts at all, it's not failing all the time. Try the information here: forum.miata.net/vb/showthread.php?t=327229
@@AmbiVe Many years ago I had a TR6 for about 6 months, it replaced a tired Fiat 124 Series 2. Traded the TR6 for a 240Z followed by more Zzzz. Eventually ended up with an NA MX5 back in 96 and still have that now (~350000km) although it's been OTR for 2 years waiting for a crankshaft fix or motor swap.
If your car starts acting all weird and such but only after you fill up with gas, remove the evap.hose from your intake manifold. Plug off with cap. From there your on your own as far as canister and hoses.
These symptoms are identical to my 93 NA thank you for this video
I hope it helps save you some trial and error!
Hi! I immediately related to your symptoms because it's exactly what I experienced in my 2002 NB (now at 102 000 km). Jerking/stalling especially under load and heat (30°C +, highway speed 110-115 km/h, then traffic slowdown). Engine would die and restart normally after those events. So I went to visually check my crankshaft position sensor (1.8 L engine). Found the plastic bracket was cracked and the gap with the pulley seems way too big! Ordering the CAS today, pretty confident it will solve this nasty problem. By the way I also had no code after those events. Thanks a lot for pointing me in the good direction!
Finally after closer inspection the CAS gap with the pulley metal tab was within specs (.032"). And the cracked bracket was still holding the sensor tight. I went to replace it anyway convinced it was deffective and sensitive to heat. But same problem showed up on test ride.
Did you fix the problem
@@Adventureswithhim Hi Dan! Replacing the Camshaft Position Sensor did fix the problem. I did my best to make it failed but the problem did not reappeared (engine stumbling, stalling and re-starting after few minutes). You have to drive it hard in hot conditions (>30°C) to prove it good. I don't expect this trouble to comme back next summer! Make sure you buy the newer version of this sensor, there are cheaper version on the market but they are the old type.
It is BOTH a cam position sensor AND a CRANKSHAFT position sensor. It is driven by the camshaft, but if it only had the cam signal, it wouldn't know where the piston was. The Miata CAS has two rows of circles cut into a disc. The outer row has 4 symmetrical slots and this is the spark signal for the four cylinders. The inner row has two holes or slots, one being 3 times larger than the other. This gives it a dot - dash sort of signal. The two inputs together tell the ecu relative piston position and which cylinder to fire.
Some CAS are Hall Affect sensors and some are optical with diodes. Both have a shutter type system. BTW, our Mazda Miata CAS is made by Mitsubishi.
Thank you so much. My 91 miata is having the exact issues you are describing.
Same
Hey man I am having this type of issue plus my rev count fails when the car dies did this happen to you?
@@WrongwayPilot My miata would stutter on the highway and get progressively worse the longer I drove until it would essentially die. I ended up replacing the air flow meter, coil pack, throttle position sensor (tps), the CAS, and both temperature sensors (one in the front and one in the back) to try to find the issue. Turns out the CAS was leaking oil on the temperature sensor behind the engine and causing all my issues. Definitely look at the temperature sensors if you get a chance. They are relatively cheap and quick fix.
@@jonahharrington7398 Thank you for the advise- funny enough my temp gauge hasn't been sitting in it's normal halfway spot, recently since I have had this issue its been sitting about 30%
@@jonahharrington7398 Hey man thought I would give an update, turns out it was alternator playing up was only charging at 13v instead of 16v so new alternator and the issues are gone atm hopefully they wont come back, haven't been on the highway yet though that will be Monday
Hope this is my problem. 89 NA Eunos. Changed the fuel pump, filter, spark plugs, plug leads, o2 sensor, drained all the fuel (thought maybe I had bad fuel as I just topped up) and no luck. This CAS sensor will be arriving tomorrow so will see if it’s any better!!
Good luck!
Thanks! Is the o ring leaking what causes the issue? I have the new circuit board for the sensor and a o ring.. would rather replace the o ring than the internals of the sensor
It can be. If you can clean it out and it works, then an oring might be enough. If not, the board is probably bad. It could also be worn out elsewhere.
Did you manage to fix it in the end?
I’m thinking I may be having CAS issues aswell. On long highway stints like 1-2hrs my 91 would stumble and cut out and eventually completely die. Soon as I restart the engine it’s perfectly fine again.
That certainly could be CAS. It's very similar to how this one would behave sometimes.
@@AmbiVe it’s a Eunos roadster I bought it about 11hrs away from home so CAS issues on top of learning to drive RHD made it an intersection drive home 😂
That sounds like a great way to build memories ;)
My cars doing the same thing! The PO put a speedyefi in because they thought it was the ecu. Going to replace this asap. Big help man!
I've been having a similar issue with my VVT swapped 91. It'd stumble at both idle and load. Since I'm running a Megasquirt ECU, there was a "sync loss 31" in the data log, which points to the cam sensor. Apparently they're prone to failure on the NB's, but from doing some research, Mazda has updated the design in recent years, so the failures aren't nearly as common.
I got a question I have a 91 NA Miata first it started jerking or stumbling when I was on highway once I kept a steady speed or once I hit certain rpms. thought their was water in fuel checked that got fuel assembly and all that replaced so it should be good. The next day went to start it left it outside for maybe 7/8 min running then I cam out and it had cut off. tried starting again it would crank over but no start
That could be ignition, this Miata got worse after running and getting warm. It could be the coil, ignition chip, or CAS. My bet would be CAS, but that's a guess without troubleshooting each part.
@@AmbiVe what's an ignition chip? Do you have the location or part number?
I used to have these exact symptoms, and eventual failure, on my 1991 v6 3.0 4Runner. It turns out that it was the Ignitor. The Ignitor & the coil are both connected by the same bracket. It was an ongoing problem for about 2 years till it completely failed & would no longer start. Oh & by the way, I do have a 1990 Miata, 1.6 that is ready for the paint job, & I'm currently waiting for the machine shop to call me, to pick up my engine block & cylinder head for me to assemble & reinstall on my miata. Anyways, while on the freeway, the same thing would happen to me as with your gal's Miata, suddenly a violent quick stall that would just as fast would reignite the engine. This was usually at 65mph or higher, so obviously mostly on the freeway. And just like your Miata, the high speed at which this would happen, would have momentum enough to quickly reignite the engine. And since my 4Runner is stickshift, it was like push-starting the vehicle but at freeway speeds. Once it left me stranded, my friend & I immediately knew it was the igniter. I ran the pre-OBD2 self diagnostics, & sure enough, it gave a code for the ignitor. I couldn't find the extra OEM ignitor that I jacked from the junkyard, so I bought one from Oreilly's. Turned on right away. I got to point out something else, a part that is similar to the Miata & the 2nd generation 4Runners. That's the AFM, Air Flow Meter, which is frequently confused with the MAF, Mas Air Flow sensor. Both serve the same purpose but the MAF was or is the newer version of the AFM, as I understand it. When this MAF starts giving problems, it can be confused with the CAS problems because they are intermitten problems...once in a while, till it gets worse, then leave you stranded. It will also have you chasing your tail...changing fuel pump, relays, fuel dampners, etc. till it fully fails & leaves you stranded. Good thing is that here in Southern California we have an abundance of junked cars, dry, not rusted nor ruined from salted snowed-in roads. Unfortunately since these same generation cars have parts that are as old as yours, the life expectancy is similar & soon enough I found myself trading in my junkyard replacement for a NAPA remanufactures AFM, which is still good today. If i ever go through these same problems on my miata, at least I know the likely culprit of the problem.
I believe this may have helped solve my problem. I'll look into getting a new CAS, so thank you very much.
Quick question just to verify, though. My NA has been doing the aforementioned things, and it has progressively gotten worse to the point of it not starting anymore. If I jump the battery, the engine stays on only if I continuously rev. As soon as I stop, it dies again. Does this sound like a bad CAS to you?
That is basically what happened near the end of this one. It got worse and worse until even revving it wasn't keeping it running long.
@@AmbiVe you are the man!! Seriously, I can’t thank you enough for your video, input, and response to my question. Much appreciated!
No problem. Good luck, I hope you get your car sorted for summer!
@@lilblingking1491 Did you get it sorted?
@@RoxusRemo yes, turns out it was the alternator bracket working itself loose and not putting enough tension on the belt! Got a new belt since the old one glazed pretty badly and it’s been running great ever since!
Good luck
Could this be why I have no spark even though i replaced all the components?
If the cas is bad will there still be spark but at the wrong time? My miata has spark and fuel but won't start
Interesting. I wonder what it is that fails inside the CAS? I have an NA6 also. And I am replacing the catalytic converter every few few years, so the car has been running rich. If there have been misfires, that would explain a lot of unburned fuel in the exhaust that is killing the cats. Now that catalytic converters are quite expensive, this does not work well as a temporary solution.
That could certainly kill cats. The CAS doesn't always fail predictably, so it could continuously be varying the misfires and burn enough that it damages the cats but runs well enough to get by.
@@AmbiVe apparently the CAS sensor in the NA6 (89 thru 83) versions of the car is an optical switch. The NA8 and later are said to be Hall effect sensors. They are pretty simple devices. There are four pins. Pin 1 is Ground. Pin 2 gets 12V. Pin 3 pulses 4 times per cam shaft turn. And Pin 4 pulses long 1 time then short 1 time per cam shaft turn. LEDs do lose brightness over time. I can imagine this producing an irregular signal, that trips the photo diode receiver most of the time, but not all of the time.
Okay. I just gave in and bought one. The NA6 has old school optical sensors. After 30 years it doesn't owe me anything.. Modern replacements have Hall effect sensors. Prices on these are all over the map. I bought a Walker for $175.
Replacement parts for the old cars is always a roll of the dice. Good luck!
I know I’m a bit behind but would it make sense for a bad cas to cause a wierd tach reading sometimes? Like sometimes it will be normal then sometimes it will be 2k rpm off and kinda lazy
I haven't seen the tach read strangely just because of a CAS. That sounds like other electrical issues, especially if it's just the tach reading and the engine isn't actually jumping around RPM. I believe that wire comes right out of the ignitor.
my 99 miata did this a couple years ago (died while driving on highway, somewhat spirited rpms) i replaced fuel pump and coil) just a couple weeks ago it died while driving on highway with ac on. would not start. waited 15-20 minutes and it started and made it home fine, no issues, about 15 miles. Any suggestions? ty
That's exactly what would happen with some of our bad CAS units. When the car cools, it will start fine, then die while driving normally.
I'm having the same issue but the only difference is that it does not sputter and there are no rough idling, it happens super seldom and only when coasting in neutral. I'm caught by surprise that the engine is already dead as there are no signs that it has died, no violent shaking etc. Any idea on what this might be? Just replaced the AFM but still the same.
I would consider the CAS or ignition. I have had that symptom when the idle transition on timing doesn't happen.
I bought a Miata from someone a couple months ago. It sat in their garage for a year, and when I got it it had bad gas, and I had to change the fuel pump. Changed it and it worked great. I let it sit again for a while because I had other stuff to work on and now I barely got it to crank And sometimes turn over. The first couple of times when I try to start it , it starts and runs decent, Then stauls. After trying to start it and keep it running it’ll die faster and faster everytime. It’ll idle less and less every time for a couple seconds. Then won’t start and idle at all. Any one having this issue?
If it will barely crank then it sounds like an electrical issue or engine mechanical issue. Is your battery good and all connections solid?
You might have several issues ranging from electrical to plugged fuel filter or injection system. Start working through each individually. Get your volt meter and check the voltage through the system and of the battery. After you know you have solid voltages and a good battery, then move to the fuel issues that might result in it dying. If the fuel system is good, then move to ignition.
Sitting is hard on cars. Good luck!
Hit the mark for me. Got engine rebuilt and code now shows up and have all the symptoms. Uneven acceleration, stumbling, hesitation, j can j feel it basically and it all makes sense now😄
A lot of these symptoms are what my 95 Miata is experiencing right now. The car would run and drive fine, but when I would put it in neutral and coast, the RPM's would drop very low and sometimes stall. This wasn't a super bad issue until just a few days ago when I was starting it to go to class, it started, proceeded to shutter and die and now I can't get it started. I am assuming its the CAS, any ideas?
I had an issue about a year an half ago with my 2001 NB MX5 where i would drive but then it started to jolt and stall, I replaced CAS didnt fix it, i replaced the fuel pump and it fixed it. BUT now im having a similar problem, i drove the car and it would jolt and stall, so i parked it in my driveway, now it wont even start, sometimes it successfully starts but then dies immediately, i replaced spark plugs, coil packs and leads still didnt fix it. All the issues seem to be CAS But how would the CAS Fail after a bought i genuine one a year and half ago..
My Miata won’t start,is it because of this?it’s slowly turns over but doesn’t do anything else
If it's slow to turn over, it's probably more likely a battery or starter issue. If it turns over without issue and is getting fuel, then it could be CAS related.
Hi thr, my 1.6 na idles good but sometimeees the rpms reaches low as 250/300 rpms, over 3000/3500 usually starts running poorly and looks like is not going anywhere, i suppose is cause a bad cas bt here in europe (in italy precisely) i cannot find anything undr 600/650 dollars, i really neet it to be replaced if it is the problem, can i import it from us or something else?
If it's just idling erratically or too high and too low, I wouldn't start with the CAS. I would check for error codes in the computer and vacuum leaks. Then maybe look at the idle control system.
@@AmbiVe that's not only the idle, i checked for codes but I haven't got any, the major problem is the loss of power over 3000 rpms
That could be a weird CAS issue. It could also be a load sensor issue, like with the air flow sensor or in the ignition system. If the load isn't being reflected properly, the engine will try to run as if the throttle is totally open or closed when it's not, tricking the fuel system into freaking out and then correcting when the o2 sensor gives the computer feedback that it's way too rich or lean.
I wonder if this could be the issue with my Miata , my 92 Miata just turns on and shuts right off ? Could this a be a CAS
One of the bad CAD symptoms we had was that the car would be running great and then just die while cruising down the road and fail to start again until it cooled down. So it could be. Bad CAS do weird things on NAs.
Quick question I have a 2006 Mazda Miata and it dies while driving, I’ve replace gas pump, the switch at the end of the key switch but still dies. I clean the throttle body too. Is automatic though does my car have that part you replace in your girlfriend’s car?
I'm not sure how the 06 is setup, but they will all have some system for ignition timing vs cam or crank position. You could look up your specific car to see how it works for sure. That does sound like a spark issue or fuel, and since checked fuel pump, my guess is either the computer, fuel pump relay, or ignition system side.
Good luck!
I’m not entirely sure if we’re having the same issue too, we just got a 93 auto for my gf and noticed a pretty aggressive jerk what seems to be around 2nd gear that it shifts too but then 3rd and 4th smooths out. Would that be a cause?
If it's an automatic and it only happens during a single gear change, it's probably a transmission issue. Miatas were never meant to be automatic, so maybe the car gods are offended? It could also be the transmission having a clutch or pressure issue.
I am having a problem when on coils 1 it will only fire once every few seconds and on coil 3 it won't even fire at all. I a new coil pack in and the same problem is accuring. Could this be the cas or would it be a crank position sensor. Any help would be very nice
I would say that it could be the CAS or possibly another portion of the ignition system or control. These CAS are so flaky, especially the Chinese reproduction versions, that it's a solid guess to start with.
@@AmbiVe I was looking around the engine and I noticed that the crank position sensor wire was ate through a little bit by the belt. The car will start up perfect and idle but as it warms up the idle will start to surge up and down. I wonder if that is the problem
You must have a later car if it has a crank angle sensor and a cam angle sensor?
@@AmbiVe yes I have a 1997 1.8l
My NB has these symptoms, though it does not immediately re-start. Takes minimum 15 minutes. One garage said fuel - replaced fuel filter ("full of rust")....but still had the problem.
When the CAS is dead or dying, often it won't restart until cooled down. We had the same symptoms on her NA.
I actually just came across this video and I have been having a no spark issue with my 90 Miata for a while now but i did have a question. If the CAS is bad will it still have power up to the coils but it wont have spark? I bought this car with 2 coil packs and i kind of doubt both of them would be bad so I'm just seeing how this system works before I buy a new CAS all together.
Correct. It won't fire a spark without the CAS working as it's not instructing the system when to fire based on position.
is there a risk of throwing off the timing when taking the CAS out and putting in a new one?
Not just doing the CAS. It is keyed to only connect one way. It is simply a pain to figure out which way that is when you're upsidedown and backwards in the engine bay ;)
Just did the timing on my 90 1.6 and at idle it stumbles/Missfires, I’ve looked at everything I can think of and I have no clue what it could be, it also has an exhaust pinging when you apply 1/4 throttle or more
Pinging like a rattle?
Hi Casper. In your opinion, how much better or what's the difference between a car that has a CTS and a car that does not need one? In other words, why does a car need a CTS?
The CAS/CTS/etc, essentially replaces a distributor that you would see in an older car. In say my Mustang, the rotation of the engine rotates the distributor which triggers a spark each time the rotor completes a circuit at each plug wire on the cap. In essence, a CAS effects the same thing, but via either triggering an individual coil per plug or through another system with control of the coils, disconnected from the actual carrying of the high voltage. Both systems are just there to allow the system to initiate a spark at the correct time for the position of a given cylinder.
I would say that a CAS/CTS is a better option overall as you have to have something filling that role to have sequential injection systems accurately in a better package. Now, if having it read a cam shaft vs a crank pully vs the oil pump shaft has a pro or con, I don't know. The SR20DET in my Z pulls it from the cam as well for it's CAS, but a lot of aftermarket systems just use magnets on the crank pulley externally to make them platform independent.
Edit: This is assuming you were talking about crank timing sensors and not coolant temperature sensors. That would be a while different can of worms 🤣
Where did you buy your CAS?
I have the same problems but it tachs then it would die. When at times I give it throttle multiple times and it would start again.I’ve changed all my grounds
I have a 1992 Miata with a 1.8 engine swap and basically whole drivetrain from a 1994 model. I had a similar issue, was driving and hit a rather bumpy patch of the road and immediately after the tach dropped to zero and it felt like the whole engine turned off while I was still doing about 40 miles an hour. The engine turned back on in like a split second. But after that incident it did it 4 more times on the way home and every incident got a little bit worse and sketchier. When I pulled in my driveway the car was idling fine but the fuel pump was making a weird noise. Almost sounds like a washing machine running in the distance if that makes sense. Does this sound like a CAS issue to y’all? Any recommendations? Thanks for any input I really appreciate it.
It sounds like you have something loose. Since it died and runs so rough, I would check that the CAS didn't move and mess up timing, that all your ignition connectors are right, your coils are tight, and your grounds are all clean and tight.
@@AmbiVethanks for the quick reply!!! That was wicked quick. Im subscribing now
My NA was running a little hot, but mostly fine... Suddenly died at low rpm while *descending* a hill... Couldn't get it to start again. Cranks hard but no juice. Faulty CAS?
Hey, any chance you figured this out? I’m having a similar issue
Great explanation. Thanks!
NEED HELP! My 96 1.8 has 179k miles! She ran great and is my daily!!! Driving to windy roads the other day when she just shut off on the highway, fuel cut and looked in the bay to see for any blown fuses or unplugged plugs!! Never left me stranded so knew it must’ve been something stupid! Get it towed to my mechanic and his diag was the CAS! P0335 code! I went and got one from a friend and still isn’t working! My mechanic says it’s now not getting spark! I found another CAS that I’m just going to buy to the hell of it for $50! I’m so annoyed! I love this car and it’s my daily! Start school Wednesday and desperate to diag and fix her! Please help me!!! I’m a junior mechanic but id rather it be looked at by a master mechanic etc…thanks!!
If you don't have spark it could be CAS, ignition chip, or coil. Each one has a specific testing process that generally just requires a multimeter and some time. Either take some time to test or open the wallet and throw parts at it. The CAS is the most expensive part, so if your friends was good, it shouldn't be as bad if it's the chip or coil.
Hi! To solve the problem descibed in my previous comment, I went to Mazda and bought a brand new CAS (BP4W-18-221B) which is identical to the one I removed. Installed it today and went for a test ride trying to duplicate previous failure conditions: external temp 30°C +, sustained highway speed preceeding a long traffic slowdown. Sure enough I had the exact same failure as before and needed to stop on the side! I was very surprised as I really suspected the CAS to be the problem. In your case, at the end and after changing a lots of parts, what exactly made you think that the CAS was at fault? Is it possible that my two identical CAS behave exactly same in heat condition? Thanks for helping me on this issue!
I received a bum CAS in the past and had to replace it again shortly after testing. It's also possible your ignition chip or coil could be having heat issues. It's hard to pin these vague issues down unfortunately.
Ok, I just went to check if I had any code recorded (I had none with the previous sensor). But now I have one: P0340 - Camshaft Position Sensor A Circuit Bank 1 or Single Sensor.
You might have a wiring issue or bad luck and got a bad new CAS. Good luck with your fix!
Ok thanks, back to the drawing board!
Hi again! Just to up-date on my 1.8L engine stumbling and stalling at hight load and temp. Because it is different from earlier 1.6L engine, in my trouble-shooting I mistakenly confused between the CAMSHAFT and the CRANKSHAFT POSITION SENSORS! Replacing the CRANKSHAFT position sensor did no good (and the old part was identical to the new). Realizing my mistake I ordered and replaced the CAMSHAFT position sensor (now this part is different from the original. Same Mazda part number but different Mitsubishi p/n engraved on the part!). I them went on a road test trying to duplicate the conditions (not easy!) which triggers a stumbling/stalling fault. It passed the test with no problem with the engine and no fault code locked on the tester. I leave just a tiny doubt for the future but I am now pretty confident that the CAMSHAFT position sensor was the real culprit! Thanks for your help!
My N/A Miata is having all the same symptoms you said but it jitters when I stay cruising at 4k rpm and then when I mash the throttle to do a pull the engine completely dies and if I hold it down it fully dies and turns off
Could that be the angle sensor or something else
Does it feel really abrupt and shake hard or does it feel like it just wheezes out and dies? It could be fuel as well. Good luck!
@@AmbiVe the shakes are very hard and when the rpms come back up it shoots back up like if nothing was wrong in the first place
I would bet it is the CAS. Ours was very similar and we replaced everything before biting the bullet and getting the CAS.
@@AmbiVe awesome thank you so much for the help and have a great one!!!
I have cylinder 3 and 4 not having spark at all. Because whenever I pull it while the car is running. The car wouldn’t shut off.(I did this test maybe twice?) I changed ignition coil, spark plugs and spark plug wire still doing the same thing. I just changed the injectors as well. Literally just 3 and 4 is misfiring. Maybe a bad CAS? I remember when I tried to change the O RING and I cleaned the cas with tons of Break Parts Cleaner and idk if that’s the cause of MAYBE the cas being broken.
If it's only specific cylinders, I would try swapping around plug wires and plugs. If it doesn't change, I might try another coil or jump to assuming that the CAS or ECU might be having issues. Cleaning it could have caused an issue, but if you looked at cleaning it in the first place, it may have been bad all along.
I have a 1990 Miata and when you give it gas it dies , I’ve replaced a ton. I actually put a new cas on the car a few months ago but I’m curious if maybe it had went out in a few months after being replaced
It may have. I have had terrible luck with these Chinese replacement parts. Even the expensive one we bought that is aftermarket seems sketchy.
Where can I get one from?
Good luck, finding a good reproduction or stock one in good condition gets harder and harder every year.
Hey man I’m having issues with my 91 NA as well. The car will start but after driving when the car is shut off the car won’t turn on again it’ll crank but no start. Sometimes it’ll start for 2-3 seconds and stall out but after waiting like 10 to 15 minutes it’ll start right up… but again if it’s turned off it’ll crank and won’t start again I have no clue if it’s my CAS or crank position any help? Thank you!
That sounds like a CAS to me. At the end that was exactly the kind of thing her car would do.
@@AmbiVe is there any way to check it? Like with a digital multimeter or? Becaus the cas isn’t cheap per say haha I wouldn’t want to spend the money of that isn’t the issue
There are a few ways, however, none of them worked for the sad CAS on our Miata. I think it would work of the CAS was totally dead, but if the car starts at all, it's not failing all the time.
Try the information here:
forum.miata.net/vb/showthread.php?t=327229
I'm more of a fan of that vehicle behind you (TR6?) and the one on your t-shirt 😬
The TR6 video that has been delayed for months will finally be redone soon, so it will be back!
@@AmbiVe Many years ago I had a TR6 for about 6 months, it replaced a tired Fiat 124 Series 2. Traded the TR6 for a 240Z followed by more Zzzz. Eventually ended up with an NA MX5 back in 96 and still have that now (~350000km) although it's been OTR for 2 years waiting for a crankshaft fix or motor swap.
All fun cars. A lot of the lower power cars are some of the most fun.
@@AmbiVe Hell yes. Love my little go kart 👍
If your car starts acting all weird and such but only after you fill up with gas, remove the evap.hose from your intake manifold. Plug off with cap. From there your on your own as far as canister and hoses.
You should have got a 3 code
I want to put a 292 in my Miata
Belt....