kevin1981

Hi everyone! I've been a lurker for a few months and have been using knowledge from the community to sort out my new to me 2004 996 C2with 90,000 miles. The car definitely had some deferred maintenance before I purchased it and I've been working through the common issues. So far I've replaced the AOS, IMS bearing (Pelican Parts bearing kit), RMS, water pump, thermostat, clutch, plugs and coils, motor mounts, and all fluids.

I've put about 1000 miles on it in the last 3 months, and 600 since completing the IMS and clutch. Somewhat recently I've noticed a bothersome engine rattle when at partial throttle. It happens in gear or not, at any speed, with engine rpms between about 2000-3500. I initially thought it might be a loose muffler or heat shield but I pulled them down to do the plugs and coils and snugged them up tight. The car doesn't smoke or burn any oil, and runs strong. The sound disappears at higher rpm and I don't hear it at idle. I'm not sure if it's related or not but I hooked my mityvac up to the connector at the intake manifold and discovered that there is a vacuum leak- so I'm preparing to do a complete replacement of the vacuum lines and components. I'd like input from you guys as to whether its worthwhile to change out the SAI valve while I'm in there. I haven't had any related engine codes, but I did have an intermittent p0430 code (catalyst system below efficiency) and I replaced the right side cat with an aftermarket unit after discovering element in the original was loose and banging around.

Do you have any ideas as to what my problem could be? I'm really hoping it isn't bore scoring..

Thanks!

Kevin

Porschetech3

Did you check your DMF real good for looseness while doing the IMS/clutch?

kevin1981

I tried to check the DMF- but I'm not sure I really knew what to expect. I could easily move the center part separately from the outer section- but it would spring all the way back to its original position on its own.

Edit: I reviewed the Bentley youtube video on DMF inspection. I believe mine is probably good.

simonsam

Hi Kevin, I have a 03 c4s and have pretty much the same rattle that i hear at partial revs. I replaced the left cat (that was rattling) and did the ims (pelican), new clutch kit, AOS same as you so those arent the problem. I havent check my exhaust or heat shields yet but it doesnt seem like it's coming from there. I bring it into my mechanic shop this Friday. Will post what i find out from the shop. Let me know what you find as well?

kevin1981

Absolutely. I plan on bringing the car to a recommended indy mechanic when I get a chance, but I'm working out of town for at least the next week.


Does anyone think this might have something to do with the Variocam Plus system? I'm not getting any trouble codes, but it seems like the rpm range might be where the Variocam is kicking in.