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Discussion Starter · #1 ·
Hey all,

Lately my 98 camaro 3.8L has been misfiring. It doesn't matter if the engine is hot or cold. It doesn't matter if idling or cruising down the highway. Every once in a while, the ses light flashes then stays on steady. Sometimes the light will go away within the same trip. When the light has come on I have tested it and gotten the P0300 code (random misfire). I have done the following to try to cure the misfire to no avail:

- Replaced Plugs and wires
- Replaced fuel filter
- Replaced PCV valve (didn't think that was it, but figured it couldn't hurt)
- Ran fuel injector cleaner through twice

When it misfires, it typically only lasts for a matter of seconds, and it seems like accelerating makes it go away. Also, its worth mentioning that it seems like it does it more when it is raining out (its hard to tell if there is a correlation with rain because I live in Ohio and its been raining ALOT lately...) I think my next step is having the ICM tested. I don't think it is the coil packs, because I feel like it would give me a specific code for a specific cylinder (ie- p0302 = misfire cylinder 2) and it hasn't. But other than that I don't know where to go. I was hoping someone on here has had similar issues and could point me in the right direction :dunno:.

Thanks
 

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Hmmm, i need to think about this one. You changed all the usual stuff anyone would change. How about the fuel regulator? It's on the fuel rail behind the throttlebody. Is the car new to you, or have you had the car for awhile.
 

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Have you checked the fuel pressure? Both at idle and driving?
 

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its coil packs or ICM 90% of the time. 3800II in fbodys requires so much god damn maintenance.
 
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The "Senior" Member
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Have the ICM tested, and if it's not that check the fuel pressure.
 
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The "Senior" Member
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Fuel Pressure was between 40-44 at all times while driving, but it never acted up while i was checking it...
Then I'd bet on the ICM. Have it tested at autozone.
 
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The "Senior" Member
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CZ's Turbo Gawd
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Icm or coil packs, don't rule out coil packs because you don't get a code for misfire on specific cylinders, its a waste spark coil system so one coil runs 2 cylinders, you can check the coils by checking the resistance on the primary and secondary windings
 
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Discussion Starter · #13 ·
Yes and so does Advance Auto Parts.
Icm or coil packs, don't rule out coil packs because you don't get a code for misfire on specific cylinders, its a waste spark coil system so one coil runs 2 cylinders, you can check the coils by checking the resistance on the primary and secondary windings
Hey guys,

Soo I took the ICM to auto zone and it passed the test. The guy doing the test seemed less than competent but nevertheless, it passed the test 3 times. I also checked the resistance on all 3 coil packs and it checked out too.

I have heard that it is sometimes possible to get a false positive on a ICM test since it isnt being tested under full load. I cant help but to think that this might be the case, but I dont wanna drop $150 on a part that wont fix my problem. Is it possible to get a false positive? Also considering how intermittently it misfires?
 

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CZ's Turbo Gawd
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It is possible to get a false positive for the reason that when tested its not subjected to the temp it sees in the car. What were the resistance readings from the coils?
 

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Discussion Starter · #15 ·
It is possible to get a false positive for the reason that when tested its not subjected to the temp it sees in the car. What were the resistance readings from the coils?
They were all between 5-7k ohms and each one was within +/- 1 of each other on both the primary and secondaries. 2 of the coil packs look original to the car and the 3rd looks like a replacement from autozone or something...
 

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CZ's Turbo Gawd
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They were all between 5-7k ohms and each one was within +/- 1 of each other on both the primary and secondaries. 2 of the coil packs look original to the car and the 3rd looks like a replacement from autozone or something...
5-7k is ok for the secondaries but if Im not mistaken the pirmary should be between .3-.6 ohms
 

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CZ's Turbo Gawd
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ok one more thing with the coils, was/is there any very faint lines (carbon tracking) on the outside of the coils? if so thats the problem, if not I would say its the ICM
 
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Discussion Starter · #19 ·
ok one more thing with the coils, was/is there any very faint lines (carbon tracking) on the outside of the coils? if so thats the problem, if not I would say its the ICM
I think it has to be a connection with one of the coil packs or something along those lines. I used Dielectric grease when I connected all of the plug wires today. It had been misfiring at least once every time I drove it lately but since I put it all back together, it hasn't acted up and I drove quite a bit tonight. As soon as I relax and forget about it, it will go at it again. I like it when things break and there is a definite fix, this is just too frustrating...
 

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CZ's Turbo Gawd
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I think it has to be a connection with one of the coil packs or something along those lines. I used Dielectric grease when I connected all of the plug wires today. It had been misfiring at least once every time I drove it lately but since I put it all back together, it hasn't acted up and I drove quite a bit tonight. As soon as I relax and forget about it, it will go at it again. I like it when things break and there is a definite fix, this is just too frustrating...
as a tech I totally preferred for something to totally break/wear out its so much easier to diagnose. dielectric grease should be used on pretty much everything in the ignition system. hell hopefully that was the whole problem now its time for a drink lol :ddbeer:
 
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