hfuglaar

I have a 2002 996 with a cylinder 5 misfire. I can start the car, in the drive way, and it runs fine with no cel or misfire.. I can drive the car, and as long as I keep driving, no problem. When I stop and idle, the cel comes on, and the car starts running rough which you would expect with a misfire. If I turn off the ignition off, let it sit a minute, and restart the car, the cel stays on, but it will idle as if no misfire. I have changed the spark plug and the coil with a new 997 coil. Any ideas? the cel is always P 0305. No other codes. After a lot of research, i thought it could be a it could be a stuck lifter, but it does clear when I turn off the ignition, but always comes back. Any ideas or things to look at?

EVOMMM

When was the injectors changed but to me isounds like a coil going bad as your motor warms up
It has happened to me with non factory parts lately companies are make shizer stuff

wildbilly32

Assuming you changed the coil and plug for the same reason(P0305): Switch the new coil to a different cylinder to see if the code follows the coil to the new position. I would pull the plug on #5 to see if it is still in good condition. Might even boroscope #5 with piston at bottom of cylinder while the plug is out.

lowpue

This is definitely what I would do....sounds like coild or plug symptoms

168glhs1986

Any resolution to this?

I took my car in for UAOS, x51 oil pan and now on my black car I'm getting cylinder 5 misfire.

They have changed out coils, spark plugs and injectors. Swapped them also. Misfire is always on 5. I'm thinking of course worse case scenerio such as something fell into the intake and then into cylinder. Car never misfired before I took it in for the UAOS to get it ready for the track.

I've asked them to smoke test the intake and do a leak down test so we can hopefully rule that out.

He is looking at replacing the cam shaft sensor next.

It never misfired for the past 6 years until I took it to them, so my logic thinks the chances of the misfire being directly related to what they did are good.

But the mechanic said the misfire is random so now that's even more puzzling.

Any thoughts on this one? These are great, well respected mechanics.

jumpy chunky

I would think that your mis fire may have been happening for a time just not enough to set CEL.

Might have been sitting at the Indies long enough to exacerbate the condition, don’t know.

I am going to say based on all the steps taken so far that there is a chance that cylinder 5 may have a lifter stuck in high lift position. Or stuck from time to time. Hard to prove without dropping engine, etc., etc.
Not sure this helps with a fix. Might want to broach the subject with your mechanic.

168glhs1986

Yes he is going to do a leakdown test. I have a feeling it's mechanical and in the head as well. Thank you for your response. I'll follow up on this thread.

168Sierra

I would also inspect the wire and connector for that coil. A poor connection ther could result in the problem you are experiencing.