I know... But I can't find a thread with a solution to my problem.

[Coy325i]

I know, old e30's frequently have a rough idle.

I have the following symptoms with my 1989 325i convertible:
* Car starts and idles okay cold, but when I give it gas it acts like it's either starving or flooding. When I get it up to 25-3000 rpms, it's fine but getting there, it makes a lot of noise - but not much power.
* It doesn't stop acting like an air compressor when the temp gauge says it's warm, it acts like that until it has come to full operating temp 10-15 minutes.
* When I come to a stop, it idles very rough (hot or cold - but not always; sometimes it idles pretty good, sometimes it literally shakes).
* When it warms up, it runs very well but it still might idle rough, as if it is loading up. It acts like it's slowly flooding.
* Pull away from a stop, and it stumbles until it clears and then runs great (1500 -2000 rpm) until you come to a complete stop again.

Plugs are all gray and nice when I inspect them. Smoke test showed no hose leaks and in fact all hoses appear fairly new. Had a real mechanic test all components separately and they tested okay. I cannot find an obvious cause. I did a tune up and replaced the fuel filter and replaced the fule injectors with 19# 4 hole injectors (didn't make any difference at all to my idle, but it runs really strong).

Can anyone explain to me how the Bosch FI system handles cold starts? I know there isn't a choke and I don't believe I have a cold start injector. Do I have something out of adjustment? I tested the ICV and it test good electronically, but I have ordered a replacement assuming it may have failed mechanically, just because controlling the air/gas at idle is specifically what it does... right?

I wrote pelican and they just said that it was high mileage, and that could be, but it runs great in every other respect except idling. In fact, it's an automatic with 240,000 miles, and it will still scratch the tires from first to second in drive; I just think it runs too good for that to be the problem... am I way off?

Thanks for any assistance.

[Sea Aych]

How's the fuel pump?
Also check out your AFM for any dead spots
Also you're right: "i" cars don't have cold start injectors

[akorcovelos]

Compression and vacuum readings will tell you a lot.

[Coy325i]

I don't know how to test the MAF sensor, but my mechanic said he looked it up on the interweb and ran the test and it passed. It accelerates smoothly throughout the range (once it clears out from a stop light) after it's warmed up. I could let it warm up in the mornings if I needed to, the worst thing is the inconsistent idle. It's driving me nuts!

I don't know how to test the fuel pump, but the fuel pressure regulator was okay too. Wouldn't that be off if the pump was failing?

So during cold start, with no cold start injector, is the idle speed controlled by the ICV?

[SmokeE30]

T a fuel pressure gauge into the system and watch it during the stumbling conditions, it pretty easy to have the wiper blade hold the gauge against the windshield while driving to watch it.

[jlevie]

Was the smoke test done properly? That would mean plugging the exhaust and replacing the AFM with a plug and nipple for smoke injection. Then oil smoke is introduced until a pressure of 2-4psi is reached and that pressure held for at least 5 minutes.

Compression (dry and wet) and leak down tests are also a necessary diagnostic.

[Coy325i]

Smoke test was done right. Haven't done a compression check.

[bad3]

it was ICV for me.

[Coy325i]

I replaced the ICV, but that didn't make any difference.

[akorcovelos]

Test the resistance on your afm, and test your tps.

[Coy325i]

The AFM tested okay, but I've ordered a replacement... That seems a likely culprit, because the problem is only there at idle and particularly ay certain temperatures (air pressure). What is a tps?

[akorcovelos]

If the afm tested OK then its probably not the issue. TPS is throttle position sensor, located on the bottom of the throttle body. It is a 3 position switch triggering idle, partial, and WOT maps in the ecu. I'm guessing your tps either needs to be adjusted or replaced. Test it for continuity per the Bentley manual (or Google).

[Coy325i]

I finally replaced the temp sensor and it idles like a swiss watch... once it warms up. When it's cold it will idle fine, but it will bogg down every time I give it gas. I shift down and feather it up to around 3000 rpm and it runs ... but not well. Not until it's run for about 15 minutes.

What controls cold starts? Do you think it could be the ECU?

[jlevie]

Cold start enrichment is controlled by the DME using inputs from the ECT and IAT sensors.

[Coy325i]

I'm sorry. That'd probably be helpful, if I knew more about this, but I'm afraid I don't understand. Also I started right off with a typo; I think , I meant ECT, not ECU.

Where is the Intake temp sensor located on a 1989 2.5L? I thought that intake air temperature was handled by the AFM.

I've replaced the Air flow meter, Idle control Unit, and Coolant temp sensor. I had the Oxygen sensor tested and had the entire system smoke tested, with no vacuum leaks. Fuel pressure is normal, so I assume the fuel pumps are alright.

I'm wondering if it might be the computer unit in the glove box. Should I just look for a good used one and see?