Rough idle at cold start/stop

[shameson]

Still haven't figured it out bump. Did some research and found a thread where it seems the op has the same issue-> http://www.r3vlimited.com/board/showthread.php?t=280197

I still have a box of some old parts/sensors I pulled off so might just backtrack. Want to see if my old tps will cause any change

[groupus]

I'm still dealing with this issue in my car. I have gotten new coils and tried them, but I am still waiting on the bracket to come (coil on plug conversion). From what I could tell, the issue still existed with the just the new coils stuck on top of the plugs, but it my need time for the computer to readjust.

Something I have considered though: I had been thinking about this as an issue that only occurs when the engine is cold, leading me to look into sensors and components that relate to the open/closed circuits. However, I had the check engine light come on briefly twice now while driving on the highway with the car fully warmed up. doing the stomp test, I get 1222 - lambda sensor reading too rich or too lean for more than 10 seconds. I think that maybe the issue exists all the time, but the computer is able to correct for it once the oxygen sensor is warm and reading the exhaust gasses.

Anyway, I'm still working on it. It's warmer out now and I have been riding my motorcycles more now, so I kinda put the car off. I will update with the next step when I get there.

[shameson]

Yes I have new coils, they are about 5-6 months old. So far this week I had no issues with this whatsoever.. The car would idle perfectly right after starting and wouldn't have excessive vibration after the idle dropped when I came to stop right after taking off. I didn't drive the car yesterday.

This morning I start it up to go to work, and of course idle fluctuates for a few seconds then settled out. Drove a few blocks down the street, stopped and it had its dramatic idle drop and weird vibration (could be worn engine mounts?) but then settles once I've been sitting there after a few seconds. When I say dramatic drop, when it starts warming and I come to stop, the rpms drop to idle rate smoothly and idles smoothly. When it's still cold it feels like the car is going to stall but it only drops to ~600 so it won't.

I got a spare ecu from a friend so I'm going to put that in tomorrow and see if that changes anything. Also ordered a new genuine ICV from BMW (employee discount) since it's one of the last sensors/valves/regulators that's not new. I should be able to get that Monday since parts is closed weekends

[groupus]

Hey Shameson, did you have any luck the with idle after replacing the ecu or icv? I've still been having the same issue all summer, but it's more tolerable since it warms up quicker now and I ride motorcycles most of the time anyway. I did play with the flap on the MAF which made no real difference. I checked for vacuum leaks again but it's air tight.

[shameson]

New icv didn't solve it. I've noticed that I can smell it's running a bit rich on start-up, so I'm really hoping a different ecu will adjust that. Didn't end up getting the ecu as soon as I thought. I have it now, so going to swap it in this weekend.

[groupus]

I tried resoldering the larger connections in my ECU with no change, but you never know if something else is bad. I have a feeling mine is running rich too. I'm going to pull the spark plugs next time its doing that to see if they are black or if its just one or more cylinders. I also want to look into what all components are in play when the car is in "open loop" mode, before the O2 sensor kicks in and it runs normal.

It might also be worth buying a cheap aftermarket chip for the ECU to see if that makes a difference (or using another stock one).

[shameson]

My next step will be to pull the injectors. I'm running mustang 4 pintle ones, my idea was maybe one is pissing fuel into one of the cylinders and flooding it on cold starts, causing it to be so rich at first but goes away after the extra fuel is finally burnt. But idk, who knows

[groupus]

Not to bring this thread back from the dead, but did the icv solve this issue? My car has been out of commission for over a year because I hit a deer and have been slowly putting it back together.
A mechanic at Bimmer Buddies near Hershey PA suggested replacing the air intake sensor and adjusting the throttle position sensor first. That would definitely be the cheaper option.

[shameson]

Not to bring this thread back from the dead, but did the icv solve this issue? My car has been out of commission for over a year because I hit a deer and have been slowly putting it back together.
A mechanic at Bimmer Buddies near Hershey PA suggested replacing the air intake sensor and adjusting the throttle position sensor first. That would definitely be the cheaper option.

I never 100% solved the issue before I sold the car. In the weeks before I sold the car, the stumbling never happened. Seemed like it was only an issue during colder weather.

[groupus]

Thanks Shameson. I'll try to keep this updated as I work through this. I know there are too many threads started for this issue with no resolution.
I tested the tps sensor, which is variable. As far as I can tell, it works right. I used to get a tps cel, but I replaced it a year or so ago when I did the intake gaskets, mess under the intake and oil filter housing gasket.I found a lot of conflicting info on that. A lot of people say the tps is adjustable, buy that is only for the m20 and maybe m10 engines. Also, the part# for the tps is the same for 90 to 2000 BMWs.
The intake air sensor is part of the MAF, so there's not much to check there. And the MAF does change resistance as the flap is moved, buy there may be a dead spot on the carbon track. It's hard to tell with just a multimeter. I'll pull that out and try to clean it up some.

[shameson]

Thanks Shameson. I'll try to keep this updated as I work through this. I know there are too many threads started for this issue with no resolution.
I tested the tps sensor, which is variable. As far as I can tell, it works right. I used to get a tps cel, but I replaced it a year or so ago when I did the intake gaskets, mess under the intake and oil filter housing gasket.I found a lot of conflicting info on that. A lot of people say the tps is adjustable, buy that is only for the m20 and maybe m10 engines. Also, the part# for the tps is the same for 90 to 2000 BMWs.
The intake air sensor is part of the MAF, so there's not much to check there. And the MAF does change resistance as the flap is moved, buy there may be a dead spot on the carbon track. It's hard to tell with just a multimeter. I'll pull that out and try to clean it up some.

My tps was set to factory spec, so I know that was never the issue. Have you ever tested your injectors? It might be worth having them flow tested to see if that leads to something. I never got the chance on my car.

[groupus]

I did pull them out and cleaned them when I did the top end gaskets, but never had them tested.

I'll hopefully get to pull the MAF this weekend and dissect it.
The next thing to try is the cam or crank position sensor.

[5Toes]

For what it is worth, my m42 has been exhibiting similar problems lately. For reference, my car does have a rebuilt AFM, rebuilt 21# injectors, new ignition coils + plugs + wires, brand new bosch ICV, foam air filter, OE BMW crank sensor, new cam sensor etc...... it has been worked pretty good.

This problem started happening after I swapped on my Dinan big bore throttle body. Its for an e36 so I had to grind down the throttle shaft so the TPS could sit the correct way (it was out 180 degrees). I ran the car for a couple months with a rough but dependable idle because I had a bad TPS that I just left unplugged. Brand new Hella TPS did not fix this problem though.

My o2 sensor is only 6 months old, but I am afraid that it is damaged from an exhaust leak where the shorty headers mate to the collector. Perhaps air has been getting in there and hurting the sensor, Im not too sure really.

I have had a check engine light on this whole time and CANNOT FOR THE LIFE OF ME get the stomp test to work on this car so I am thinking my engine harness is questionable. Going to check for continuity between DME connector and TPS this weekend.

TLDR: TPS sensor or o2 sensor. leaning towards TPS since stomp test wont work

My long term solution... is going to be a custom new harness and ECUMASTERS standalone.

[roguetoaster]

Toes, if I were you, I'd look at the wiring at the TPS connector before doing anything else. Pull the boot back and check that the wires are actually intact.

If you turn up some other issue that seems like it could impact other M42s do let us know.