car doesn't want to idle correctly

[mspiegle]

This is on my 181K '87 325is.

A few days ago, my car was idling very poorly. It would go from 500rpm to 1000rpm and back down again. I swapped the AFM from a '90 325is over, and that didn't help much. I found a hole in the intake boot and a cracked vacuum line to the emissions bypass device. I replaced the boot with one from a '90 325IS and had to bring the ICV over as well because the boot and ICV were physically different. I also replaced the vac line to the bypass valve. After this, the car's idle was much steadier, but still very rough and only idling @ 500rpm.

Now, if the car is cold, it will start PERFECTLY and very fast. It will run for 7-10 seconds, and the idle will begin to get rough. After another 10 seconds, the idle is VERY rough, and the car is trying to idle at around 500rpm. I have replaced the above mentioned parts, as well as O2 sensor and ignition coil (everything else in the ignition system is fresh and been replaced within the last 2500 miles).

I ran through the chart of ECU tests in the bentley. That confirmed that my TPS was working properly, and lots of other stuff should be within spec as well.

Where should I start looking now?

[mspiegle]

I'd also like to add that the engine appears to run fine off-idle (revving by hand).

[mspiegle]

Would also like to add that unplugging the ICV nearly makes the car stall until I plug it back in.

[mspiegle]

ARG, i keep forgetting details... I have a recurring CEL (that I didn't have before). If I reset it, it will come back.

IIRC, you can't read the CEL codes on '87 and earlier cars - right?

[mspiegle]

Ok, apparently I can do the 'flashing CEL' thing per the bentley manual.... here's a video of some strangeness:

http://raptor.nauticaltech.com/videos/check_engine.mov

I turn the car to the ON position. I press the gas pedal 5 times. The light blinks once, then goes out for 3 seconds. It flashes once, flashes twice, then flashes more than 4 times. I thought the codes only went up to 4?

[325ise30]

Yup you can get codes from your car, instructions for this are in your bently book (I beleve they are displayed the first few secondes with the ignition on engine not running). I would check you coolent temp sensor and your ox sensor does not come into play when your engine is cold. Just wondering are you running bavauto wires?
As you can see in gen tech ive got my own idle problems thred to. (A very common bmw problem!) Well hope this info can assist you.

[mspiegle]

Running the IE wires. I have the same wires on my '90 IS and they worked great before the car met fate. I figured out the CEL thing, but i'm getting codes that the bentley manual doesn't cover (strangely..).

I think i'm going to swap the brains next and see what happens....

thanks for chiming in my thread

[RobertK]

Have you checked your TPS yet?

[mspiegle]

I went through the table of ECU checks in the bentley. I checked and verified that the TPS has working idle and WOT signals.

[mspiegle]

Ok... this is strange.


I swapped the ECU with my '90, and I noticed no difference. I decided to drive the car around anyways and see what happens. As I pulled out of my driveway, the car almost stalled, then the CEL came on. I drove the shit out of the car on the street and now it seems to be idling much better (at around 650). I swapped back to my regular ECU and the car did the same thing... ran like crap, threw a CEL, I drove the shit out of it, and now it idles normally.

I'm letting the car rest now to see if it still runs this good when its cold or warming up.

[golde30]

e30's run like shit when u reset the ECU. it will run like that while the ECU "learns", which is usually like ~5mins.

[mspiegle]

Yes, but they usually don't keep throwing CELs while "relearning". Are there only 4 things that can cause a CEL? (the 4 codes listed in the bentley), or are there other things as well?

[ddongbap]

Its better if your ECU learns from scratch. A cold start I mean. And you're sure that theres no other leaks from after your MAF, to your throttle body?

[mspiegle]

Its better if your ECU learns from scratch. A cold start I mean. And you're sure that theres no other leaks from after your MAF, to your throttle body?

i've tried it hot and cold, throws a CEL no matter what. I'll check for vac leaks again tomorrow. Maybe I just need to replace the intake manifold gasket and all the injectors seals to be sure...

[jht3]

you can use throttle body cleaner to check for intake leaks. squirt it along the edges of gaskets and if the car bogs down you've found a leak

i did this on my S14 and found my throttle body gaskets were leaking. it idled and ran worse when cold than it did once it fully warmed up. the thermal expansion was sealing up the leak