#5 Cylinder Misfiring???? - Team Camaro Tech
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post #1 of 6 (permalink) Old Apr 7th, 03, 02:47 AM Thread Starter
Join Date: Apr 2003
Location: Mass.
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Ok, I have a 1997 Camaro RS (3800 engine) and was wondering if anyone has ever dealt with a problem like this....

Ok, basically my number 5 cylinder is misfiring...I'm not entirely sure why it is, but it is. I have already changed out the Mass Air Flow sensor, the left bank O2 sensor, and the Intake Air Temperature Sensor because all of the above were given by the error codes from the computer...none of this has seemed to help at all in any way. Actually it seems to be getting worse and worse...

A little background on what I think might be a partial cause would be that I currently have an SLP cold air intake on the car. One day driving to work my car startin misfiring and I found out that my filter had fallen off the tube...I put it right back on before I went too much further and tightened it up again and it hasn't fallen off since then but then the car progressively got worse. Now before it would happen mostly when it was raining...or damp or whatnot, but now it's happening all the time and it's not letting up...any advice as to what I should do would be greatly appreciated. Thank you!!

I posted this in the 2003 tech forum above too...probably shoulda just posted it here...sorry for the duplicate.
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post #2 of 6 (permalink) Old Apr 7th, 03, 03:18 AM
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None of the stuff you changed out would cause or cure a misfire on one cylinder. Misfires will wreak havoc with trouble codes since they make the engine low on power and the exhaust too rich. The computer will try to balance out the mixture by leaning out the engine (or bank) but since your pouring raw fuel into the exhaust from the misfiring cylinder, it's impossible and the computer flags the most likely culprit with a trouble code.

Have you checked the spark plug, plug wire, and ignition coil on this cylinder? If it's not one of these three things, then it may be something mechanical like a bad valve, valve spring, rocker arm, a wiped out cam lobe or low compression.

I think that your engine has three coils doesn't it? Generally, but not always, if you lose the spark on one cylinder, you lose it's mate on the other side of the coil. I think #2 fires opposite #5 on the 3800??

Good luck,

Paul D.
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post #3 of 6 (permalink) Old Apr 7th, 03, 03:26 AM Thread Starter
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Yeah, I did replace the spark plug wires..that was the first thing I did actually. Didn't help a bit...I'm starting to think it might be the 5/2 coil..You're right it does fire 2 and 5 on that coil...
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post #4 of 6 (permalink) Old Apr 7th, 03, 07:45 AM
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The GM ignition module set up fires both cylinders for every coil at the same time, everytime. That is to say regardless of wether it is time to fire cylinder 2 or 5 they both get the spark. It doesn't take much energy to fire the cylinder which is on the exhaust stroke, so for design considerations to keep the system simple it just fires both. So if you suspect a DEAD coil, or loss of input to the primary side of the coil both cylinders 2 and 5 will misfire or not fire. It is possible, though quite rare for a broken terminal at the secondary side of one of the two cylinders on the coil, either 2 or 5. But you can swap the coils easily with one of the other two coils for troubleshooting.

I agree nothing other than the plug wires so far could have caused your problem, but it's always good to check the easy stuff first. If you find that cylinder 2 and 5 are both misfiring, then you need to dig deeper into the iginition control sytem, including the computer, crank trigger, ect.

But I would start by asking is it misifiring under load only? Or worse under load, or does it misfire running at idle in nuetral? Also does it seem to mifire right from the start, or only after it's warmed up?

If it is misifiring worse or only under load, that is in gear accelerating, I would run a static AND dynamic compression check first, including the snap throttle check. This will eliminate anything mechanical with the engine, especially valvetrain items. Remember the static compression check only tells you the sealing condition of the engine, the dynamic check will tell you it's breathing ability of individual cylinders which is why this is the check along with the snap throttle test will tell you what you really need to know. The static test is only a baseline.


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post #5 of 6 (permalink) Old Apr 7th, 03, 08:26 AM Thread Starter
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Actually, I just went out during lunch time from work and bought a new ignition coil from AutoZone and replaced the 2/5 coil and guess what...NO misfires!!!! Everything now seems perfect! I still have the O2 Sensor and Air Intake Temperature Sensor unplugged for now, but I'll get those put back in tonight when I get home and get the chance to throw my car up on jacks...I started the car up after I put the new coil on and then reved the motor and it didn't misfire. I then took it for a quick drive around the parking lot and got on it a little bit and again, NO misfire...it seems like that has to have been my problem. As for the way I found out the number 5 cylinder was misfiring was through the computer diagnostic...the 2nd cylinder could have been misfiring too, but as it stands everything seems 100% better...we'll see how it stands up on my way home...Thanks everyone for all the help!!!

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post #6 of 6 (permalink) Old Apr 7th, 03, 12:07 PM
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I'm glad to here it was just the coil. I had a similiar problem on my 96RS. I bought a spark plug tester (basically a sparkplug with a clamp on it) for $10 and checked each sparkplug wire. Turned out the #2 and #5 cylinders were not getting a spark. I switched the position of the 2/5 coil with one that was working, and then both coils were not working. I switched the coils back to the original postion and only the one 2/5 coil was bad. By doing this I realized I had to get a ignition module as well as a new coil. So $200 dollars later the problem was fixed.

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