Popping Noise While Driving
 

My 944 started making a sort of popping noise while driving the other day. The noise seems to disappear when coasting (clutch dis-engaged) or when the car is out of gear (even if I rev the engine a bit). Frequency of the pops is correlated with speed (or maybe RPM it's hard to tell as it's not entirely consistent). At one point, it seemed like the sound was coming from the rear, but later I wasn't so sure. There was one moment when it sounded like the "popping" was occuring with the clutch dis-engaged (possibly during a turn), but I was not able to reproduce this.

From reading Clark's it sounds like it's probably not the clutch or torque tube (since it doesn't occur in neutral). Unfortunately, Clark's doesn't offer any diagnostics for narrowing it down further other than replacing things. Any guesses as to what the problem might be? Any further tests I can do?

Check the easy stuff first.
A"popping" sound from the tailpipe?
Repack your 4 CV joints. The "popping" sound may be a "clunking" sound. Maybe swap R to L.
Check for transaxle fluid-fillup if needed.
Check the bolts on the TT to transaxle coupler. Torque to spec.
Do you still have the rubber clutch disc?
Are your lug nuts tight?

GL
John_AZ
1988 924S + 1987 924S

I went out for another spin just a few minutes ago to try and further isolate the source of the sound. Unfortunately, the sound has stopped for now. This does make me wonder if this was actually an engine problem (backfire?) since due to some vaccum and/or temp sensor issues the engine tends to run noticeably better when it's rather cool like it is right now (my test earlier today and the initial onset of the problem were in the afternoon when it was much warmer).

The one thing that doesn't seem to fit with that is the sound persisted when I let off the gas completely with the car in gear. From what I understand, the DME cuts fuel completely once the idle switch trips (until you get down to 1200 RPM, 1600 for later years).

For repacking the CV joints, anybody have experience with any of the cheesehead kits on Amazon? I get the impression the Lisle ones stink, but there are a few others.

No experience with Amazon kits. Unless your CV boot is cracked and leaking-just remove the drive shaft, put on latex gloves, grab a lot of rags, and remove the grease on the joint and in the boots. Repack and put a gob in the center of the mounting plates of the rear axle and transaxle.

http://www.pelicanparts.com/catalog/shopcart/944M/POR_944M_SUSaxl_pg1.htm

If you cannot get a quality 12 point set locally from NAPA, Sears,or a Snap-On tool or MAC distributer, try:

http://www.baumtools.com/catalogs.php OR
http://www.zdmakautotools.com/wbstore/main.asp

GL
John_AZ

if it is a pop pop pop coming through the exhaust it is definately the afm i replaced mine with a used one and this subtle backfiring or popping sound stopped