horrible s50 idle, please read, I am sick of this

[rede30]

Just for clarification, my idle surges from 1-2 but does not get low and want to die. I tossed in a new TPS and AIS today and it didn't do anything. I thought I had an extra engine coolant temp sensor (blue top) but I didn't so that coudl still be bad. I dont get why that would cause a surging idle though. I have also tried a good DME but that didn't help. In the midsts of turning the car on and off while testing stuff the motor, once, chilled at 2K and did not come down until I turned the car off.

Any chance that there is a fault in the wiring to the alternator/starter. It may be load cycle that you are getting due to an intermitent loss of continuity at the alternator.

I should check this.

[Farbin Kaiber]

What about the high/low A/C switch? That will cycle the idle too, IIRC.

[motorsports_3]

My car is doing the same thing. I just finished fabbing the intake today and plugged in the MAF and if surged from 1-2k but wont die. When I unplug the MAF it stumbles around 500. Have you been able to figure this out?

[motorsports_3]

Anyone

[motorsports_3]

I have had no luck tracing it so far

[rede30]

I have not figured it out. Have not had time to mess with things. I want to plug in a MAF to test things but don't have a spare, I don't have many more things that could be wrong.

[motorsports_3]

I got mine figured out, the throttle cable was too tight and the throttle body was a bit open. I manual closed it and the idle drops to 500 and stays. I also sprayed the springs with some lube to loosen them up.

[rede30]

I actually spent awhile yesterday doing a few things. I didn't get anywhere. I have a 95 325is parts car so I tossed in some sensors but nothing is different.

If I rule out a bad sensor and intake leaks, where do I go next? Could my alternator be bad or getting intermittent power and would it cause a surging idle? Actually, what could cause intermittent power anywhere in the system and why would my idle stick at 2 once in awhile.

she is also breathing really hard. Lots of air is being sucked through the intake. Could anything but a vac leak cause this? I am going to get a smoke test just to be sure, I have to. I am just scared my head is cracked at the intake mani since all the hoses are new and inspected and shot with carb cleaner. And no it is not my brake booster.

[Jason89i]

did you align you tps? check the e36 bentley for ohming out the tps at 0 throttle input. jason

[rede30]

did you align you tps? check the e36 bentley for ohming out the tps at 0 throttle input. jason

The e36 bentley seems to think they are not adjustable.

[Farbin Kaiber]

Another short in the harness?

[Jason89i]

The e36 bentley seems to think they are not adjustable.

the e36 bentley shows the tps ohms for throttle off. if memory serves me correctly..... there are two screws that hold in the tps. you can loosen the tps and rotate it until the throttle off ohms are correct. also check to make sure your throttle plate is fully closed. shin a flashlight around the plate to check for ANY gaps. ive seen two bigbore throttle bodies with less than perfect sealing that caused a bouncing idle. jason

[mongule]

Any update to this?....my swap does the exact same thing. Mine is OBD2.

Brand new ICV, TPS and no change

The alternator suggestion is interesting.

Basically if i wait long enough the ecu adapts to a normal idle ( a bit high but no fluctuation) and as soon as you hit the throttle it goes up to 2k and stays there.

[M3 euro ltw]

Dme?

I'd be very concerned about the ICV and the DME running it. Assuming that you do have a good ICV, (and if you've only tried one off a non-running parts car, you may have two bad ones on your hand....), then I'd wonder about the drivers on the dme being blown....not too far fetched after a short.

Have a buddy drive over, and see if your dme runs his car properly, or borrow his dme if that is easier.

Also, consider disconnecting the throttle cable completely to make sure all tension is off, and inspect for being cracked open as mentioned.

Sorry for WOB if you've already checked this out, but that is where I'd be suspicious.

[Fusion]

I'm just going to throw a guess here - is the engine->body ground wire ok?
I've heard weird stories of them causing mayhem on various cars.