"check engine" problem, 88 325is

[Eliminator]

Hello all,

My 88 325is has been having a problem. The check engine light will illuminate and stay on continuously. When I reset the computer (unplug) and start the engine, the come back on again in 15-20 seconds. i believe this is normal behavior when there's a fault. The problems are: 1) I cannot retrieve any fault codes, not even an OK. It has a 173 ecu, so the stomp test should work, correct? 2) Generally, when I park on a downhill slope, the "check engine" light will be off when the engine is re-started. it will then stay off for several hours.

When the light is on, the idle seems to be *slighty* worse, and sometimes it's slow returning to idle. I have checked the TPS and coolant temp sensor and they are OK. I've also replaced the O2 sensor, it runs better but the check engine light still comes on. The idle stabilizer *seems* to work. Fluids are all topped up as they should be, and I have not been able to find any vacuum leaks.

What should the resistance be on the AFM, open and closed? Mine seems to work, resistance varies between 2000 and 3000 ohms.

I am suspecting either a bad AFM or a bad computer (since I can't retrieve codes). What do you guys think?

[Eliminator]

Anyone?

[e34john]

i have kind of the same problem. check engine lights comes on sometimes and it starts running rough, othertimes it runs pretty good. i did the stomp and had the no error so im confused. changed everything that i could do cheap oil, filters, plugs, o2 sensor, etc.

[Eliminator]

i have kind of the same problem. check engine lights comes on sometimes and it starts running rough, othertimes it runs pretty good. i did the stomp and had the no error so im confused. changed everything that i could do cheap oil, filters, plugs, o2 sensor, etc.

I can't get any codes to display at all, so I'm even more confused. I've tried the stomp test about 50 times and it just won't work. I have the 173 ECU, so it should work, correct?

How exactly are you doing the stomp test?

[Eliminator]

John - Check your canister purge valve. Try tapping it with your finger or a wrench and see if the CEL goes out. If not, there's a test procedure in the Bently.