Engine note different after Clutch Replacement

[Tak]

Any help from the 944 crowd on this one?
I just finished putting a new clutch (+ pressure plate, TO bearing, TO guide, pilot bearing, fork shaft, and fork bearings) into my fun car (89 944 S2). I did the work carefully following the manual procedure (Ooof that was painful), and now my car sounds different...it now has the classic beetle rasp to it.
It seems to run fine, but I'm reluctant to romp on it until I identify the sound--any suggestions out there?
Pertinent facts:
-Car ran fine when it went into my garage with violent shuddering when letting the clutch out.
-Car was on jack stands for 4 months before I got to it (long story)-battery ground disconnected entire time.
-Clutch problem was a detonated pilot bearing that spilt it's balls and cage into the cluth bits. Disk and plate were fine (but replaced anyways), TO guide was worn, TO bearing sounds dry but spun easily.
-Included in the process were removing the exhaust, unplugging the O2 sensor, and removing the reference mark sensor.
-No issues with disassembly and re-assembly of any components.
-Battery dead. Overnight charge and car would crank ~1 revolution and all lights go dim. New battery and car started first try. The alarm didn't even complain!!!
-Car goes well (didn't rev over 3k or use more than 50% throttle). Brakes feel like they take more force than I remember.

BUT, car sounds like a beetle (actually a little deeper, like a 2.0l Vanagon)
Makes the noise stationary or moving. Changes with revs, stationary or moving. No backfire on deceleration.

I felt around the exhaust flanges as best I could, and don't feel any gas leaks.
Using an auto stethescope, I can NOT pinpoint a noise source (listened to all four exhaust runners, intake runners, 8 spots on valve cover, balance shaft housings, water pump, alternator, bell housing, and starter. I did not listen to the torque tube.

HELP. Any suggestions welcome. I'm a rotor head, so these piston thingies confuse me!

Thanks,

Tak
#29 ITA Rx-7
SFR SCCA

 

[Quickshoe]

Any CEL codes? If it isn't a serious issue it might have to go through a number of off to operating temp cycles before it throws a code.

Disclaimer, it is late and I am just thinking out loud. I don't know much about 944's other than they should not sound like a beetle.

 

[924Guy]

Does it rev well, or like crap? Sure you didn't induce an exhaust leak? Or even an intake leak?

I'm trying to remember back to when I helped do a clutch on an S2 (once and only time)... biggest screwup I remember was inadvertently disconnecting the MAF (air plumbing, not connector) when tilting engine to reengage torque tube...

 

[Tak]

Well the mystery continues, but appears to be resolving...
2 more start and warm up cycles and the engine note is back to normal. I drove it 40 miles this morning on the freeway. At the beginning of the trip, low end torque was down (50-70 mph in 5th gear was noticably off), but it revs out just fine. At the end of the trip, the low end torque was improved.
I'm going to guess that with 4 months of no power, the computer lost all the trim values, and it is slowly rebuilding those values... Sound reasonable?

I suspect the odd engine note was unusually retarded ignition timing while the computer figured out how much advance it could put in.

Thoughts?

Tak

 

[Quickshoe]

Sounds reasonable to me...again not being familar with 944's not sure how their ECU logic works.

Could be a bad ground that just happens to be "good" now.

Crank angle sensor loose?

 

[lateapex911]

man, I had one of those cars, and if that happened to me, I'd be scred to death., LOL. That kind of thing makes me get nervou$... Glad you are working it out.