Ricky_D

I just experienced two CEL with misfire cylinder in a week. First time was four cylinders, and today only two.

I had the belt replaced last week with some other maintenance, just saw it is Conti belt. According to this thread, it seems like it might be the issue.

Can misfire damage the engine in any way? Should I ask for belt replacement?

BTW, I believe the idle is a bit rough (shaking the car a little).

Thanks

1996 993 C2

2ndof2

So here's my VERY late update:

I never did look further for vacuum leaks but I did have Porsche OE belts installed. This did NOT solve the misfire issue. About 3 months ago my battery finally gave out. I went with one of those gel based standard sized ones from Sears that are suspected as being rebranded Odysseys. Would have purchased an Odyssey but couldn't find one in my size at the time. (My brother is a yacht captain and swears by them) Anyway, some time went by...then some more time...then some more...and all of a sudden I realized....huh...no CEL for misfires in quite a while. I have no idea if the battery really solved it but its a helluva coincidence if not. I'll keep my fingers crossed that things continue this way for a long time! So perhaps batteries have some influence over the misfire codes coming up...who knows?

nine9six

I know the thread is old, but I do not want to recreate another when a perfectly good thread exists...

Is it conceiveable misfire codes could be traced back to bad or weak battery ground?

techman1

Yes. Main battery ground cable. Clean and replace. Better yet buy a new cable at your FLAP.

2ndof2

Another update: Misfires still happening periodically. Its looking like worn DMF at this point per my mechanic and Steve Weiner's comments, but not big enough issue to change out just yet. Just have been resetting the codes with my OBDII reader when it happens.

nine9six

Huh? Whats a FLAP?

I'm tempted to see if the CEL resets itself after several drive cycles; but I have to admit to not being very tolerant of looking at a glaring CEL, regardless of the culprit...

BesideTheBox

nine9six and 2ndof2 - Are you only getting the CEL light or is the engine also running poorly before the CEL comes on?

I'm thinking that if you just get the CEL and the engine is running fine, then the DMF may be the issue and it is affecting what the flywheel sensor is reporting to the computer. This is being picked up as the small changes in engine speed that are the input to misfire detection.

When I had misfires over a year ago, not only did I get the CEL, but I also had the flashing CEL (imminent damage to CATs according to documentation). When I cleaned up all the grounding points, the CEL went away and has not come back in 7K miles. I wish I knew which grounding point cleaning fixed it, but I did not test after cleaning each one.

My guess at FLAP - Favorite Local Area P-dealer?

nine9six

Car seems to be running fine; but every so often (every couple of months), at idle, I will feel a brief roughness (maybe 10 seconds), even through the gear shift ****. It's a good thing I have not had the flashing CEL, as that is a, "Danger Will Robinson" kinda notification.

While I am leaning towards the DMF as the cause, I would like to exhaust and rule out the cheaper potential culprits, first. If not, I can feel an RS clutch kit and LWF, coming into view...If this is the case, then thats when I'll do the wires too.

P.S. Thanks for the definition on FLAP... I'd have never guessed

PRSWILL

When I first got my 993 it threw this code 2-3 times in the first 1000 miles. It had sat for a very long time ( years) and then I ran 4-5 tanks of 93 + octane thus it and put 2000 miles on the car and it runs better now than ever-!no codes . Run good gas you can foul plugs with these cars and I'd bet that's part of the issue especially if your car burns a little oil. Mine does not burn oil, but my last 911 did and it would run on a bit with low octane gas