Ben in Plano, TX

Guys,

Thought some of you might be interested in this.

At a DE this past weekend my 97S (60k Miles) threw a check engine light twice. Our local dealer had a tech at the track with a Porsche tester and he read the codes for me both times (and reset the light). Codes were misfire cylinders 1,2,3,4,6 both times.

I also have a pretty noticeable clakkity, clakkity, clakkity noise coming from the tranny vicinity only at idle and only when the tranny is very warm (having just come off a 25 minute session on the track). Tech listens and says "that's your dual mass flywheel starting to fail". Apparently when the fluid in the DMF gets very warm it makes the noise and the 'wobble' from the DMF is sufficient to throw off the movement of the pistons - thus the 'misfire' codes from OBDII. More precisely, the tech tells me the misfire code is generated from readings taken from the teeth of the flywheel - so if a DMF is degrading and wobbling a bit it can generate the codes.

So I ask "ok - when do I really need to correct this?". He says when it's no longer clakkity, clakkity but becomes bang, bang, bang! you need to fix it. I asked if letting go til then could cause more damage in the tranny and he seemed to doubt it would. So I'm not in a big hurry but I do see an RSCS clutch and flywheel upgrade in my not so distant future.

Regards,

Ben

Rick Lee

60k miles sounds good to me. How long have you had this car and how do you drive it? I look forward to DIY'ing a DMF and RS kit, but don't want to have to do it anytime soon. I'm at 34k miles and drive it like I stole it. I don't think it makes any noise, but others may differ. I'd love to se a poll on the lifespan of DMF's.

Fred R. C4S

After you install a LWF and RS clutch, you will still heard a clackity clack coming from the transmission when everything's warmed up. It's just the gear rattle the dual mass flywheel was designed to eliminate. Nothing to worry about, but it is a surprise the first time you hear it.

Cheers,

Ben in Plano, TX

I've had the car since 2001 @30k miles. I'm the first to track the car and I drive it daily as well.

Probably 2k of the 30k miles I've put on it have been at the track - I don't flaunt the law but drive moderately aggresively on the street.

I suspect it'll be a long time before I have to replace the DMF. But I'll probably do it preemptively now that I have an excuse for the warden.

I agree that the clackity clack noise is gear noise - and since the DMF is supposed to dampen gear noise and now it's not doing such a good job I think that's why the tech says it's beginning to go. By comparison all the other 993 drivers I was around at the DE had silent trannies after run sessions - and several of them flog the car harder than I can just yet.

This doesn't bother me in the least - but a number of 993ers have posted about CEL at DE's and I thought they might be interested in another reason why you might get a CEL at a DE and not under street conditions.

Ben

George A

Ben,

I was told it was DMF on mine by the same person but after replacing it, the CEL still came on. It worked for Bob G. but not me. The ISV was my problem.

George

Ben in Plano, TX

George,

The info came from Cliff.....

I've cleaned my ISV some time back and it seems to operate normally.

Do you still have DMF? Do you get gear noise after run sessions? KC was out at MSR as well and his car doesn't have the gear noise mine does.

I also get a 'clunk' when I shut off the motor - purportedly another sign the DMF is going.

Where were you last weekend, anyway?

ben

ps: got down to 1:33 for my best time - a long way off you guys I know but maybe next year we'll have some fun out there in the same run group. Glen ran a 1:18 in his new cup car!

George A

I was there Friday (in the wife’s car) but my car wasn't ready, so I skipped the DE.

I still have the DMF and I've never really noticed any “unusual” noises (before or after). Yes, the same person told me the same thing. When they replaced it, they told me it (DMF) was bad but two weeks later I got the CEL again. Last time I saw Kevin at the track, he experienced the CEL phenomena. Did you ask him how he solved it?

At what RPM did the fault codes appear? Mine were always around 800 rpm.

George

Ben in Plano, TX

George,

The codes did appear at idle ~ 800 rpm. They showed up after I had cooled down from a run at the next (or time after next) that i restarted the car.

Before one session I jumped in the car - started it - no codes. Shouted at Cliff "Hey, no CEL!", triumphantly. Drove up to grid - shut it off - got back in 5 minutes later - started up - and the CEL comes on!

I'm not sure the DMF is causing the CEL but I'm pretty sure the DMF is starting to fail. I get a lot of gear noise when the tranny is hot (didn't have this before) and the shutoff 'rattle' is getting more pronounced. BTW - I just had 60k service and I had the tranny oil flushed & replaced with Mobil1 75w - same stuff I put in at 45k miles - and the report on the condition of the tranny oil was that it was clear & clean. Still think that the DMF could go another 20k miles for all I know....

I don't know that KC ever did get a real 'solution' to his CEL - just that he had it reset a couple of times.

Ben