325i (1991) Idle Issues

[pimp_mobile]

Hi All newbie here... I've had a quick trawl through the past posts but couldn't see one that quite matched my issue.

The Car - 325i - 1991.

The Fault - when the car is cold it struggles to find and stay at 600-700rpm. Eventually it gets there but not until its bounced about abit. Also when you're driving along it tends to stall/nearly stall when you come up to junctions. Generally this occurs when cold though sometimes it will occur when its warm.

Also when you disconnect the battery/ECU the fault goes away for a while and then returns after a day or so.

Things Checked and changed so far:-
All pipes etc checked for leaks - none apparent.
Changed the ECU
Cleaned and changed idle control valve
Changed temerature sensor
Changed ECU/DME relay
Changed throttle position switch
Changed mass air flow meter
Run injector cleaner through the system

I've read somewhere that it could be a fuel supply problem. Also read that some of the earlier models had another widget that controlled the ICV.

Any clues/ further suggestions? Cheers in advance...

[Pete159]

I can at least confirm that you a right about earlier models having another widget. Around 1989 there was a separate Idle Control Unit, located on the left side (glovebox). After that (1990) the idle control is included in the Engine Control Unit (ECU).

[dannyboy759]

Had the same problem on one of my cars, it was the AFM, could see if you could borrow another one and see how that works

[pimp_mobile]

Cheers Pete, I won't go hunting for another black box with wires sticking out of it!

dannyboy, if by AFM you mean air flow meter, I think I've already swapped that, though the one that went on came from an earlier model, but still had the Motronic ignition system. But I'll double check with my bro which meter I've got on at the moment.

If I disconnect the ECU and let it reset itself I get at least a day of wonderful joyful BMW motoring... Not sure why it takes about a day to return with the issue though. I've not tried the "stomp" test yet, might try that later on in the week.

[Speedtouch]

Stomp test only works on US models with a 'Check Engine' light!

Might be worth changing the fuel filter.

Also, if your ECU is a 380, change it for a 173 - the 380 has extra diodes in the idle control circuit that are reknowned for blowing.

[pimp_mobile]

Cheers SpeedTouch... have fuel filter waiting to go on...

Both ECUs were 173s, though I think the original might have been chipped at somepoint as it handles a little different to the spare. I forgot to check whether it had been opened up when I had it off.

[pimp_mobile]

OK fuel filter changed, in general running much better, but still a bit stall-y. I've read on a couple of threads lately about "training the ECU" is this age specific/ ECU Specific? Was trying to work out whether I needed to run the procedure or not.

Also are there special high performance fuel filters that can be bought. The part we pulled off that looked like it might be a fuel filter didn't match the replacement. When I get chance I'll stick a photo on here to see whether anyone knows what it is.

[wullie325i]

i had this on my last car and it was the ignition coil as the pin on one side had split completely and was only held on by the thin wire inside.

[pimp_mobile]

Done the coil already and all the plug leads... At some point I will run out of parts to replace... or hair not sure which yet!

[hongkongfuey]

I can at least confirm that you a right about earlier models having another widget. Around 1989 there was a separate Idle Control Unit, located on the left side (glovebox). After that (1990) the idle control is included in the Engine Control Unit (ECU).

would mine have that on a 88 325 with 173 ecu?

[hongkongfuey]

I can at least confirm that you a right about earlier models having another widget. Around 1989 there was a separate Idle Control Unit, located on the left side (glovebox). After that (1990) the idle control is included in the Engine Control Unit (ECU).

would mine have that , 88 325 , 173 ecu

[pimp_mobile]

Sorted...

Having cleaned the injectors out and changed the fuel pressure regulator, and altered the base idle air fuel mix. Its finally done, running like a dream

Think it was either the mix or the injectors in the end.