2008 GMC Acadia Single Cylinder Misfire Part 1
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- เผยแพร่เมื่อ 25 ก.ค. 2024
- 2008 GMC Acadia Single Cylinder Misfire Part 1. This car has low compression on cylinder #3. Lets use first look sensor and in cylinder pressure transducer to find our problem.
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Great video...you really are getting much more confident with these sensors and what they can tell you about the condition of an engine....a volumetric efficiency test of this engine would be interesting to see too.....hope you feel better soon...looking forward to pt 2
Thank you my friend. Part two is coming soon. Cheers
Great stuff!!! Part 2...Can't wait!!!
Thank you my friend. Part two is coming soon. Cheers
Great job! Hope you get well soon.
Thank you my friend.
PICO scopes are great tools. You have some other nice tools as well...and skills to back them up!
Thank you my friend. In my opinion Picoscope is by far the best scope comes with price but is lifetime investment.
Very interesting Ramon
Thank you my friend. cheers
Thanks Ramon for your video.
You might want to ac-couple your map sensor to get a more meaningful /interpretable waveform. It will almost mirror your first look sensor if you do ac-couple the sensor. I suppose you're using the DITEX FLS, I also do ac-couple them as well.
I agree with your thought process, the not opening intake valves or another restrction do cause an extrem negative pressure in the cylinder on the intake stroke and at the same time there is no suction in the intake manifold so the pressure rises there.
If this was an GDI engine TOTALLY carbonized valves come to my mind but then probably other cylinders would be affected as well, at leat partially.
Something maybe impedeing the correct opening of both intake valves ......
I guess a standard running compression on the bad and a good cylinder would have pointed into the same direction....
Friendly greetings, Juergen
I do AC couple my signals sometimes but this time I was able to see my problem with DC voltage. Part two is coming soon. Cheers
Very nice video Roman.
Thank you my friend. Part two is coming soon. Cheers
Great experiment -- so revealing to see all the three sensor waveforms side by side. The in-cylinder pressure waveform seems to be the most informative, but that begs a question -- what percentage of modern cars have hard access to the spark plug holes?
Get well, Ramon!
Thank you my friend. This engine was not that difficult to get to spark plug holes but it would be easier if my problem was on front bank. Cheers
Thanks for the video. My question sir. With the intake sensor are you looking for a pressure spike or a vacuum dip when intake valve opens. Cause it seems like you would get vacuum dip but instead you get pressure spike could you please explain 2hats goin on inside intake manifold please
Each time an intake valve opens the corresponding cylinder is connected to the intake manifold . The intake manifold with the engine shut off is exposed to atmospheric pressure .
When the engine runs the downgoing pistons create a low pressure - also called vacuum and sometimes negative pressure - and through the open intake valves this negative pressure is transmitted into the intake manifold. Each cylinder creates one negative pressure pulse. With the engine idling and the throttle plate closed this vacuum generated by a sound engine at sea level is around 17 to 21 inches of mercury.
Negative pressures for historic reasons are measured differently than positive (above atmosphere) pressures and these 17 to 21 inches HG equals to ~ 8 to 10 psi. The MAP value would result in:
15psi (atmospheric pressure) minus10 psi (vacuum created by the engine) equals 5 psi.
If this engine had a compression ratio of 1:10 the running compression of a cylinder at idle should be around 100 psi. (10 psi is what the engine is sucking in, times 10 for the compression ratio.)
When accelerating, the throttle plate opens further and more air rushes through less restriction into the intake manifold and into the cylinders. So at higher rpm/throttle opening the pressure in the intake manifold increases. Nevertheles, each cylinder on it's intake stroke still does create a negative pressure pulse.
As Ramon showed in his video the MAP sensor translates high (atmospheric) pressure into high voltage and low pressure (negative, lower than atmospheric) into low voltage.
The first look sensor does only show changes in pressures, Other than the MAP sensor the FLS does not measuure the exact pressure and displays it. Therefor the FLS is also called a differential pressure sensor, it detects changes in pressure but the signal size does not neccesarily correspond to the physical size or quantity.
Wether a first look sensor displays pressure increase as a spike or as a dip depends on its design. There are ones which do it one way and ones which do it the other.....I do have sensors from the same manufacturer and some display the other way around. When using one , just make sure to know how the sensor works. If you prefer to see pressure as spike and your sensor showed it as dip you always can invert the signal with the scope software.
Finally, if for any reason an intake valve doesn't open there will no negative pressure pulse be generated by this cylinder. As the air keeps flowing into the manifold in this instance the pressure will rise in the manifold..
HTH
juergen scholl wow thank you for all that info. Im trying to really understand engine performance. I appreciate reply
Can I be your student? Are you in Kentucky LOL ? Thank you so much for this explanation you are awesome my friend.
an intake valve.... you can do an old fashioned bleed down check see where the air is going
Yes sir that test would reveal this problem. Thank you.
i did not hear any lifter noise nor chain ?suspect bent intake valves
Yes sir we definitely have restriction on intake. Thank you.
Hoping people struggling with gm 3.6 misfires. Flashing on startup only. After weeks of diagnosis time permitting... Turned out to be dilated pins on coil pigtails check those its a problem. Tighten them with small side cuts carefully.
Dialated sorry for mis spell
That is a great tip. Thank you sir.👍
Sorry for the poor spelling on my post. It was late when i did that. So it was supposed to say check engine light and dialated not dilated!! Now theres more to this than meets the eye...four wire coils theory and operation ill call it work completely different than a two or three wire coil setup.im still trying to "get it" but dont full understand it quite yet. The three wire coils i could use a noid light to see if the driver is working properly. Now the four wire coil works as a separate module each somehow. So in our instance the brown wire connect s coil to coil to coil etc. So our number 6 coil wasnt fully connected to to dialation till warm! So next guy in line kicked to the curb giving us 1-3-5 misfire on startup. So anyhew... Often overlooked dialated pins on coils and injectors costs techs and customers tons of time and money. See lots of new coils and misfire still happening.hope my loss of time educates someone and wow hours of time and loss of sleep for a 5 minute repair...lol
Nevermind you e
Explain it