I know this is older, but a few questions/comments. What injectors are you running? Any chip/tune? If you dont have a chip/tune, the stock ecu targets 672rpm idle. If you are idling higher than that with IAC disconnected, then the ecu will keep closing the IAC trying to hit that rpm until the IAC is completely closed. That might be why you dont get an rpm change when unplugging the iac. What I noticed is that your AFR is running ~12.5 when you do the hot start. Rich like that can contribute to surging. In your older videos before you opened the throttle body, notice how the engine settles down after it goes into closed loop, bouncing around 14.7afr. Also, TPS between 0.7 and 1.2v is all the same. If its in that range, no need to mess with it. ECU reads lowest tps voltage every time you turn the key on.
Very interesting results. I have a build similar to yours andI was having the same exact issues with warm startup idle. Did the same thing with opening the throttle body and now no longer have the idle issues. I still think what the problem is the stock ecu is always trying to bring the ilde back to the stock idle of something around the 600 to 700 rpm ( which the engine will not run at that low of idle with a cam). At cold startup the IAC is wide open so it is out of the picture until the motor is warmed up. At warm startup the engine puts the iac into play to try and bring the engine back to the stock rpm which causes the surging for the first few seconds after startup.
I just sent my computer back to FoxResto so they could confirm if it’s OK. They will put in one of there cars to try it out. I’ve owned this car for 4 years and never had an issue with this surge until earlier this year. It’s a head scratcher but I’ve not given up yet. I would prefer to get the idle back down like it use to be, around 850.
Funny I had a white 90 FOX and now a Braun van like in your background. I totaled my GT almost 25yrs ago paralyzing me but someday I'll have another. Great looking ride you have.
Hi. Thanks for the comment. I’m sorry to hear about your accident and I hope you are able to get another Foxbody some day. Have you ever come across the TH-cam channel from HandDriven? He utilizes a wheelchair and is working on a Foxbody project. In our case, my son was born with several medical issues and he is non-verbal and requires a wheelchair. Having the accessible van is amazing.
@@thefoxlife3431 i'll go check him out. Yes a van is a God send. For me it's freedom to go again. I can't wait to see what all projects you get done this winter. Hopefully you'll get the issue solved with it not starting when it's hot.
Seems like the settings i suggested may have Fixed your Cars issue. Man im Glad for you...cause I know how you were feeling. I saw all your diagnostic vids before i saw the issue..then i wrote you a comment. Give it a few spirited drives including some safe WOT pulls..... ... reset the idle 50 RPMs lower if any objectionable surging while driving/ ideling at stoplights. A9L are actually only supposed to be 850 Max in its programming.. but mine is at 900-950ish and happy.... ..then reset the Computer if you change it....then let it learn for a while..to get the fuel trims tightened up with drives and ideling...and start enjoying it again. Good luck 5.0 family.
Thanks for the suggestions. It definitely help get me back on the road. I don’t think this fixed the problem but it helped work around it. It doesn’t make sense to me that the throttle blade was the issue since I didn’t mess with it before the issue started. It idled at 750-800 for a couple years without issue and then just started dying all of a sudden this summer. My driving season is about over so I’ll send the computer back to be tested and see if it has something wrong.
@@thefoxlife3431 hey..thanks for the reply.. and be proud of your efforts...you have a Nice Ride. I also have my extra A9L out to get new caps and whatever it needs. It went fuel pump prime always on...and 1 capacitor was loose with one lead burnt off. Capacitor would just lift off. Keep me updated with what you find.
@@thefoxlife3431MAN I LOVE YOU FOX AND I LOVE MUSTANGS AND I CURRENTLY HAVE 8 CARS IN MY COLLECTION ANYTHING FROM A COUPE COBRAS AND MY 4 SHELBYS AND 2 SUPER SNAKES AND MY Z28 AND HONESTLY MY FAVORITE IS MY FIRST MUSTANG I BOUGHT BACK IN THE 90S IS MY 87 MUSTANG GT WITH T TOPS AND IT'S NOT THE FASTEST CAR IN MY COLLECTION BY A LONG SHOT BUT FOR BACK IN THE 90S IT WAS A PRETTY FAST CAR THAT I LOVE TOO DRIVE AND I WILL NEVER SELL.
Interesting. It’s 2am now. Will have to really think about what could be the issue. What in the world would cause a hot soak no start concern but could overcome it by adjusting the idle higher? Idk. Got to go to bed
I sent me computer back to tue place that had replaced the capacitors. They tested it again and said the ROM chip was over heating and causing the issue. It isn’t something that can be replaced. They said it will get worse over time and probably stop working all together. I bought another A9L and had the caps replaced on it and had it tested. I’ve got the new computer but I haven’t installed it in the car yet. It’s supposed to be the fix but I’ll see how it works once my winter projects are done.
Actually no. When I first insta Ed the new computer it seemed like the issue was gone but that has changed now that I’ve been driving for a while. I’m still clueless.
@@thefoxlife3431Did you check the fuel injectors? I think your A/F is giving you a clue. If you are in California an emission test will confirm. You could take an IR temp sensor to see if one or more of your headers are cooler than the others. My (expensive) hint is if you go to the trouble to change the injectors change out the injector harness with one from LMR/Scott Drake
I'm with you on the IAC Not doing shit. I have done the same thing on a car I'm having idle issues with and with an IAC on the car and another one plugged in-it doesn't move at all under any circumstances. I've tried everything 20 times. No change.
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I know this is older, but a few questions/comments.
What injectors are you running?
Any chip/tune?
If you dont have a chip/tune, the stock ecu targets 672rpm idle. If you are idling higher than that with IAC disconnected, then the ecu will keep closing the IAC trying to hit that rpm until the IAC is completely closed. That might be why you dont get an rpm change when unplugging the iac.
What I noticed is that your AFR is running ~12.5 when you do the hot start. Rich like that can contribute to surging. In your older videos before you opened the throttle body, notice how the engine settles down after it goes into closed loop, bouncing around 14.7afr.
Also, TPS between 0.7 and 1.2v is all the same. If its in that range, no need to mess with it. ECU reads lowest tps voltage every time you turn the key on.
Do a base idle reset. Works everytime.
Very interesting results. I have a build similar to yours andI was having the same exact issues with warm startup idle. Did the same thing with opening the throttle body and now no longer have the idle issues. I still think what the problem is the stock ecu is always trying to bring the ilde back to the stock idle of something around the 600 to 700 rpm ( which the engine will not run at that low of idle with a cam). At cold startup the IAC is wide open so it is out of the picture until the motor is warmed up. At warm startup the engine puts the iac into play to try and bring the engine back to the stock rpm which causes the surging for the first few seconds after startup.
I just sent my computer back to FoxResto so they could confirm if it’s OK. They will put in one of there cars to try it out. I’ve owned this car for 4 years and never had an issue with this surge until earlier this year. It’s a head scratcher but I’ve not given up yet. I would prefer to get the idle back down like it use to be, around 850.
What heads did you go with? I went with Trick flow 11R heads with a comp cam.@@thefoxlife3431
A step in the right direction.
Funny I had a white 90 FOX and now a Braun van like in your background. I totaled my GT almost 25yrs ago paralyzing me but someday I'll have another. Great looking ride you have.
Hi. Thanks for the comment. I’m sorry to hear about your accident and I hope you are able to get another Foxbody some day. Have you ever come across the TH-cam channel from HandDriven? He utilizes a wheelchair and is working on a Foxbody project. In our case, my son was born with several medical issues and he is non-verbal and requires a wheelchair. Having the accessible van is amazing.
@@thefoxlife3431 i'll go check him out. Yes a van is a God send. For me it's freedom to go again. I can't wait to see what all projects you get done this winter. Hopefully you'll get the issue solved with it not starting when it's hot.
It’d idle real low at stop signs or stop lights or even stall and I’d have to feather the throttle a little to start it. I have a 80mm throttle body
Seems like the settings i suggested may have Fixed your Cars issue.
Man im Glad for you...cause I know how you were feeling.
I saw all your diagnostic vids before i saw the issue..then i wrote you a comment.
Give it a few spirited drives including some safe WOT pulls.....
... reset the idle 50 RPMs lower if any objectionable surging while driving/ ideling at stoplights.
A9L are actually only supposed to be 850 Max in its programming.. but mine is at 900-950ish and happy....
..then reset the Computer if you change it....then let it learn for a while..to get the fuel trims tightened up with drives and ideling...and start enjoying it again.
Good luck 5.0 family.
Thanks for the suggestions. It definitely help get me back on the road. I don’t think this fixed the problem but it helped work around it. It doesn’t make sense to me that the throttle blade was the issue since I didn’t mess with it before the issue started. It idled at 750-800 for a couple years without issue and then just started dying all of a sudden this summer. My driving season is about over so I’ll send the computer back to be tested and see if it has something wrong.
@@thefoxlife3431 hey..thanks for the reply.. and be proud of your efforts...you have a Nice Ride.
I also have my extra A9L out to get new caps and whatever it needs.
It went fuel pump prime always on...and 1 capacitor was loose with one lead burnt off. Capacitor would just lift off.
Keep me updated with what you find.
@@thefoxlife3431MAN I LOVE YOU FOX AND I LOVE MUSTANGS AND I CURRENTLY HAVE 8 CARS IN MY COLLECTION ANYTHING FROM A COUPE COBRAS AND MY 4 SHELBYS AND 2 SUPER SNAKES AND MY Z28 AND HONESTLY MY FAVORITE IS MY FIRST MUSTANG I BOUGHT BACK IN THE 90S IS MY 87 MUSTANG GT WITH T TOPS AND IT'S NOT THE FASTEST CAR IN MY COLLECTION BY A LONG SHOT BUT FOR BACK IN THE 90S IT WAS A PRETTY FAST CAR THAT I LOVE TOO DRIVE AND I WILL NEVER SELL.
Interesting. It’s 2am now. Will have to really think about what could be the issue. What in the world would cause a hot soak no start concern but could overcome it by adjusting the idle higher? Idk. Got to go to bed
Not sure what is causing it thinking maybe the cam and computer fighting each other to idle
mine did this alot, ignition control module on the distrubuotor was bad
I have gt40 heads and a b303 cam and I’m having the same issue
Did you end up finding out what the issue was? I have a 94gt that’s now doing the something
I sent me computer back to tue place that had replaced the capacitors. They tested it again and said the ROM chip was over heating and causing the issue. It isn’t something that can be replaced. They said it will get worse over time and probably stop working all together. I bought another A9L and had the caps replaced on it and had it tested. I’ve got the new computer but I haven’t installed it in the car yet. It’s supposed to be the fix but I’ll see how it works once my winter projects are done.
@@thefoxlife3431the verdict was the computer in the end
Actually no. When I first insta
Ed the new computer it seemed like the issue was gone but that has changed now that I’ve been driving for a while. I’m still clueless.
@@thefoxlife3431 so you right back where you was..... I'm scared I did everything you did..... Crazy part I been messing with this shit 2 years tho
@@thefoxlife3431Did you check the fuel injectors? I think your A/F is giving you a clue. If you are in California an emission test will confirm. You could take an IR temp sensor to see if one or more of your headers are cooler than the others. My (expensive) hint is if you go to the trouble to change the injectors change out the injector harness with one from LMR/Scott Drake
I'm with you on the IAC Not doing shit. I have done the same thing on a car I'm having idle issues with and with an IAC on the car and another one plugged in-it doesn't move at all under any circumstances. I've tried everything 20 times. No change.