Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP
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Do you have a vacuum gauge?
we was working on this a few weeks ago and i gave up to finish my jeep. no i am back to finish.
i already did vacuum, compression, leak down, and switched injectors
What is your vacuum reading and is it steady?
Do you have a noid light to confirm that the PCM is opening injector?
15psi steady and yes checked noid light on injector and spark plug
MY suspicion is that it is mechanical in nature.
it only happens after car runs for 5-10 min
ant the last thing i did before i got this code was take timing cover off to change gasket and seals
has a compression or leak down test been performed?
both and good
Does your engine have AFM or DOD, V8 runs in 4 cylinder mode?
If so, cylinder 6 is an AFM cylinder and probably has a rotated valve lifter.
they do that in 1996?
Not sure if your has it, but you have exhausted all other testing paths.
Compression will test average, valves operate while cranking.
Can you run the engine with the valve cover off please?
You are the second customer I have had today with same problem.
GM started this concept in 1981.
i just took it for a ride to get code to come back on and do leak down test while hot.
when i hook air up and cran engine over by hand there is no air coming out either valve??
now code is random misfire
will take valve cover off tomorrow
So you had a P0306 (Cylinder 6 misfire) and now you have P0300 (Engine misfire detected).
Your engine is a V8, isn't it?
This code was not present prior to taking the timing cover off, is that correct?
Did you drop some gasket residue down the intake ports by accident?
how bout opti vent check valve being clogged
Is the P0306 definitely gone now, and is only a P0300?
I would say you possibly had some residue under some valve seats and it is clearing out now, it may come good.
Did you have the intake manifold off as well as the timing cover?
No. I believe that check valve closer to the optispark I put on backwards I just drove it around for 20 minutes no check engine light so far
Ok, it may have been a combination of things, but ultimately was still a vacuum leak, hence the last code of P0300, versus the cylinder 6 specific of P0306.
Great you found that with the check valve.
Is it a good system, but fraught with problems as they age.
Hope you all good now.
Go out and give her a good run now.
Hopefully good from cold start as well.
well i was wrong went to drive to work today after 5 min p0300.
left it home all day cleared codes let it run til code came back now p0306
idling between 620-680rpm
any chance new opti is damaged or i ruined it
If this only happens once it warms up, does the misfire stay there while it is idling?
We need to be sure whether the injector pulse is dropping out, the spark is dropping out, or it does have a valve not operating.
What does the spark plug look like after it is has been missing like this?
exhaust is sucking in air on both sides. valves?
Yes, sounds like exhaust valve not seating.
Black from fuel, but poor combustion due to lack of compression.
taking a break from this for a few days to finish my jeep.
then i will resume the repair
I hope my advice has been of assistance to you.
Wishing you all the best.