random idle missfire

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Mar 11, 2011 | 09:09 PM

j_tizzle_84

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random idle missfire

engine is from 2000 camaro m6

been having rough idle recently so i hooked up my scanner and it is missing on multiple cylinders. it not enough to set a code or even show it in the miss history but is noticeable. i have changed plugs, cleaned fuel filter, checked fuel pressure, changed 02s, done compression test, cleaned mass air flow, did crank variation relearn
fuel pressure is 57 at the rail
compression is 170 cross the board
data viewed on modis scanner and genesis scanner
o2s are switching
fuel trims at idle are 0 stft and 0 ltft
fuel trim cell is 16
my thoughts
1) i have msd 8.5 wires what is life expectancy of these they are kinda old.
2) is it plausible for multiple coil to fail i know its possible but is it common for these coils

Apr 1, 2011 | 04:26 PM

j_tizzle_84

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ok replaced plug wires didnt fix it. reset pcm didnt fix it. did induction cleaning didnt fix it. now it is getting worse. it now misses between 1500 and 2000 rpm pretty bad. i plugged in the scanner and it shows a pretty good number of misses on all cylinders. please help starting to pull hair out.

Apr 1, 2011 | 08:06 PM

joecar

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From: So.Cal.

How big are the misfire current counts...?

Also do this:
- leakdown test;
- cooling system pressure test;

(to see if any coolant is getting into the cylinders).

Apr 1, 2011 | 08:09 PM

joecar

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From: So.Cal.

Check all coils for spark using a spark tester:

Do you have access to an oscilloscpe...?
Get voltage/current waveforms for all cylinders:
- secondary (will show kV and duration).
- injectors (will show injector pintle movement (back emf)).

Apr 1, 2011 | 08:10 PM

joecar

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From: So.Cal.

Are you sure you have no airleaks (and that your PCM is going into CL)...?

Apr 1, 2011 | 08:10 PM

j_tizzle_84

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cylinder 7 was like 248 couple in the 100-150 one was 5 i will write down exactly what cylinder is what tomorrow when i get in the car. just remember #7 was bad

Apr 1, 2011 | 08:13 PM

j_tizzle_84

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Quote:

Originally Posted by joecar

Are you sure you have no airleaks (and that your PCM is going into CL)...?

its definitly going into closed loop as i am watching on scanner. as far as air leaks doubt it unless it is the manifold.which is coming off sunday to check and clean. as well as leakage test, pressure test and a known good set of coils from my buddies cts-v

and no access to oscilloscope would trade left nut for one right about not

Last edited by j_tizzle_84; Apr 1, 2011 at 08:19 PM.