Yes, an idle thread.

[GrantB]

Hey guys, forgive me if this has been already covered, i've googled, searched on bimmerforums and on this site for an answer but all the threads seem to have different symptoms. so here i go,

-Car had a little bit of a miss when idling when it ran for a few minutes.
-Took out the ICV and MAF and cleaned those bad boys out and they are sparkly clean ( i think this is where i screwed up)
-Took off the throttle body, cleaned that all up as-well.
- Plugged in all plugs, hoses.

Now when i try to start the car, it starts then it instantly dies. i unplug the MAF, it idles fine. when the car is running i plug it in and it just dies no way to stop it from dying.

I cleaned the ICV and MAF when carb cleaner and let it dry for about 15-20minutes. Before i cleaned the MAF it idled, with it plugged it idled a bit rough, but just ran better when it was unplugged so i thought cleaning would do the trick but now it has caused me more problems. Hopefully you guys can englighten me on what the MAF exactly does in an m20b20 and how to diagnose it properly rather than just plugging it in and unplugging it.

Thanks all for your help, anything and everything will be appreciated.

[staysideways]

In m20s they are not MAF they are AFMs and it stands for air flow meter i did the same as you and cleaned it but i had made everything worse it would fire up then choke

1989 E30 325i Sedan Alpine

[staysideways]

What i found out is that my icv was faulty but i have a m20b25 with a 1.3 motronic. The icv change did nothing until i unplugged the battery for 15 mins and let the pcm have a fresh start it fires right up idles perfect and throttle response is good too

1989 E30 325i Sedan Alpine

[packratbimmer]

The AFM is a potentiometer that sends a resistance signal to the ECU for fuel enrichment.

[GrantB]

UPDATE:
I unplugged my battery for 15-20 minutes with everything plugged in and reconnected the battery, fires right up. The idle problem is still there, sounds like its missing. i disconnected the ICV and the idle did not change, started the car up with it unplugged idled like it was missing plugged it back in, still the same. So is my ICV toast? thanks

[RoDo]

UPDATE:
I unplugged my battery for 15-20 minutes with everything plugged in and reconnected the battery, fires right up. The idle problem is still there, sounds like its missing. i disconnected the ICV and the idle did not change, started the car up with it unplugged idled like it was missing plugged it back in, still the same. So is my ICV toast? thanks

Turn your key to ON but don't start the car, if your ICV buzzes and slightly vibrates it should be good.

[GrantB]

UPDATE: The ICV buzzes and vibrates, i unplug the AFM car dies. now i am moving onto timing. Will update when i have results

[GrantB]

Anything else that could cause a missing idle? I have checked the coil, seems to idle a bit better. while reving it, it Misses. Not the plugs, wires , distributor. Could it just be strictly timing? Thanks

[packratbimmer]

I just changed out my injectors and my bad idle and noxious fume problem went away pronto. The car was gassing out the block on start-up and would not move until warmed up.

There are a hundred variables to look at, but I often ask myself - would I take a dirtbike way out in the woods with dirty 25 year old clogged jets???

[GrantB]

Hey guys update again, checked the injectors and it runs shit when each unplugged so those are all good. The shitty idle only seems to occur when the car is first started up, when it runs for about 5 minutes the missing stops and idles fine. Reving it and it doesn't miss. Is that just the cold start? Does the m20b20 have such thing. Electrical sensor or vacuum? Thanks

[packratbimmer]

That is exactly what my car was doing. Are you getting serious fumes on start-up? Mine was really bad. Could smell it inside the car with the windows up. Car would not move for a few minutes. Injectors corrected the problem instantly!

The injectors can be functioning and still be clogged, mismatched, leaking down and/or shooting a bad pattern.

Also, while troubleshooting, realize that the DME is adaptive so changes often happen gradually. In other words, it might take a few run cycles for corrections to "level" out.

[GrantB]

no i don't have any really bad fumes on start-up. Ill take out the injectors and see if the o-rings are torn or anything like that

[packratbimmer]

OK - Just realized you have an m20b20. Do you know of your car is L-Jet? Might say on the DME. If so, you probably have an cold start valve in the intake (top passenger side). It has a temp sensor/timer associated with it (located in the thermostat housing) and might be tied into the idle module and/or DME - not sure. Some temp sensors had different timing in terms of seconds open. The sensor might have the # of seconds stamped into the brass?

That is exactly what my car was doing but it is a 1989 325i Motronic 1.3. I am in ME and we are still getting pretty low overnight temps. Are you getting serious fumes on start-up? Mine was really bad. Could smell it inside the car with the windows up. Car would not move for a few minutes. Injectors corrected the problem instantly!

The injectors can be functioning and still be clogged, mismatched, leaking down and/or shooting a bad pattern. You could put a pressure gauge in-line to see if the injectors are leaking overnight and dumping a bunch of raw fuel on your pistons that has to burn off after cold start. Keep in mind that a bad check valve and general leaks could also cause a pressure loss as well. I have pulled the rail and injectors in the past to see if my injectors were dripping (they often were). Stock M20 injectors are not that reliable, especially when looked at over a 30 year period.

With that stated, you could be having the opposite problem - you might be running lean on start-up due to a clogged cold start valve, bad sensor, wiring issues or improper sensor for your climate. Might need to open the cold start valve longer especially in winter.

[GrantB]

UPDATE:
replaced the injectors, no change. The idle seems to get better quicker. Could it just be the TPS, or just the cold start. where is this exactly located? (the cold start) Also no CEL