rough idle when cold, need ideas.... Fixed Finally!

[mcgrath]

when the engine is cold I get a rough idle. After it sits and runs for a few minutes and the water temp guage gets near the normal operating mark, the car just instantly starts running perfectly smooth. before it runs smooth it runs rich as hell too. The O2 sensor checked out ok. I thought I read somewhere that these m20's don't run right if the water temp sensors are bad. I do in fact have one that the terminals broke off of when I was doing my engine swap. it is the one that uses spade terminals. in the etk software its part number: 12631279722 could this be a problem? they call it a temperature switch in the software. I went ahead and order the switch just in case that was it but could there be something else i'm missing?

the engine is an 84 325e

Thanks
Steven

[mcgrath]

I changed the water temp sensor. part number 13621357414 in the etk. thought it might help but it didn't. could it possibly be a bad ecu? I did a search and didn't find hardly any info on solving this problem. if someone has any info on fixing this please let me know.

[mcgrath]

I cleaned the throttle body out today too see if that would help. nothing changed, but i forgot to hook the vaccum hose back up to the air boot in between the afm and tb and the car fired right up. had a lower rpm then normal then it when up to the normal idle. has some surging when i step on the gas. Does this tell me anything or am i still pissing in the wind? the temp switch comes in today i'll test it out later today.

[bkelsey86]

check your cold start valve. If it doesnt work your car will start off running rough.

[NORCAL/E30]

^^^ will cold start valve make your idle fluctuate. My car does'nt run rough but the idle goes up and down between 600-900 RPMs when I first start it. Not just when its cold but almost everytime. Not a threadjack. Just seems like a similar problem. :)

Thanks, ABE

[KenC]

^^^ will cold start valve make your idle fluctuate.

No

[mcgrath]

the new sensor didn't help, but I adjusted the screw on the afm and icv and that helped out alot. it still has a roughness on acceleration until it gets warmed up. I will check the cold start valve in the morning.

[mcgrath]

Just firing up and old thread to see if anyone has any ideas on what is wrong with this engine.

Since the time of my first post I have changed the rest of the temp switches and sensors, upgraded to a 535i AFM, changed my ICV, and upgraded from an 021 to the 027 ecu. I still have the same exact problem as I had before. I have the cold start valve bypassed right now but it didn't make any difference, (just takes a few more cranks to start now) I got a multimeter and checked the TPS it is functional.

[jht3]

intake leak?

try carefully spraying carb cleaner around the intake parts like throttle bodies, hoses, etc. if the idle changes for the worse you've got a leak

[mcgrath]

thats one thing I didn't bother to check. I will go give it a quick try before I go to bed.

[mcgrath]

nope didn't do anything. I sprayed everywhere. I think it's fuel injection related because It will get to the same spot every time on the temp guage and smooth out no matter how hot or cold it is outside. when i get to florida I will test all the wires going into the ecu unless someone has another idea for me to try.

[mcgrath]

Finally fixed it today. Thanks to FL for having a decent slection of U Pull it yards. I was able to get the one thing I hadn't replaced on the car, which was the entire engine harness. Pulled the harness and installed it today. The car fired right up and didnt miss a beat cold or warm. Looks like fuel milage is already getting a little better.

[Efterlyst27]

How much did they charge you for the engine harness?