Exhaust valve flap?

[LagunengrunE36]

I have a '90 325is. Recently, it's been having weird idle/power issues. When I start it in the morning, the idle is pretty rough. It jumps between ~500 and 1k RPM and the car shakes. Taking off is pretty rough, too. When I let the clutch out, it feels like the gas pedal isn't really connected. I give it gas and nothing, and then all of a sudden, the RPMs jump. Driving in 3rd gear around 25-30, the car is very rough and lurches. When I push the clutch in, the RPMs drop, it feels like it's gonna stall, and the RPMs jump back up and after this cycle repeats a few times the idle stabilizes. This mostly goes away once I drive around a little and the car warms up. When I sit and idle normally tho, the check engine light comes on and the idle becomes erratic again.

Today, driving home from school, everything was fine. Then close to home, the car began hesitating when I give it a little throttle. I get on the gas a little bit, and it gets power, loses power, etc. all in the space of a few secs. When I give it more throttle, it stops doing this, but it feels like it's lacking power. The engine light came on, and whenever I pressed the clutch in, it would basically stall (all the lights on the dash come on) and then suddenly the RPMs would jump up to 1k or so. Changing gears was really rough, etc.

So I get home and check the codes. It's throwing 2 codes: "Vehicle speed signal not present" and "Rear exhaust valve flap"

I guess the speed signal refers to the sensor on the diff. I did take the diff out a few months ago, and the clips on the sensor were very brittle and broke. It's possible that it backed out over a bump or something. I'll check it tomorrow once the rain stops. Could that really cause those issues tho? I'm lost on the exhaust valve flap.

Any ideas?

Thanks.

[jlevie]

To the best of my knowledge, the DME on this car doesn't get a speed signal from the differential. And there is no exhaust valve flap on any E30 (that is found on E46 cars). If you are reading the codes with a diag tool not made explicitly for an E30 (OBD I system) you aren't going to get valid results. If the TPS on the car is working correctly you can get the fault codes via the "stomp test".

My first suspicion, given the description, is that there are intake leaks possibly accompanied by a sticky ICV and/or a bad TPS. A smoke test of the intake will tell if there are any intake leaks and where they are. The ICV can be removed and cleaned and the TPS can be tested and replaced if necessary. You might also be faced with a clogged fuel filter and/or a dying FPR or fuel pump. The tests for those are in the Bentley manual.