85 318i idle problem

[318cody]

http://youtu.be/ycnd7-P_YXI

Hello all, this is my first time posting on this forum. I've been experiencing Idle problems since I bought the car over a year ago, now that she's pretty much restored and the head is rebuilt I would like to get it registered but it won't smog like this. I have no idea what could be the cause. She starts up fine, idles for about 10-15 seconds and then drops and surges and continues to do so steadily. It has no hesitation or loss of power through the gears, and it sometimes feels like it's effected by the brake or clutch (very lightly). A bmw mechanic went through her checking everything for two weeks and was unable to locate what's causing it. ICV,02s,MAP, TPs, Temp switch, and vacuum lines seemed to all be good. he mentioned a few other computers he checked but i didn't get a list of which. One more thing, unplugging the TPs does even out the idle. Anyone out there who might have any ideas?? It would be greatly appreciated! thanks, cody

[Deadskittles]

Welcome! Seems very odd and i know you already said ICV was good but did you try removing it altogether and plugging the lines? My ICV was "ok" but it would still mess with my idle a lot. Not saying this is exactly it but if you haven't tried this is think its worth doing.

[318cody]

No, i haven't tried removing it all together, but i have tried putting in a working one with no luck. :/

[Deadskittles]

Mine was "working" too, they just don't seem that great. Also did you check your Idle control unit? I've heard those are touchy. (Btw im not sure thats the official name) Im talking about the little green and yellow box near your ECU.

[89 e30]

Smoke test... Looks like you have a small vacuum leak

[318cody]

Just worked on her a bit, First the TPs. I tried to set it higher, and it will do a steady surging idle from 1100-1300 and even out at 1.5k. Then I tried bypassing the ICV and it started revving up to 2500, so i'm assuming that does indeed work. Did a soapy water test and there's no vac leaks. The mechanic I took it too checked out everything in the glove box area. stumped!.. still haha thanks for the ideas though!

[89 e30]

You cant always find a vacuum leak with soapy water or carb cleaner, there are more places where a vacuum leak could be than the hoses you see on the intake

[Smelser]

Propane also works if yo udont smoke. just dont blow yourself up, and do it OUTDOORS as any propane that doesnt get sucked into the vac leak will settle in the lowest part of the garage, like CO does. its heavier then air.

[Hey_You]

Best thing to find a vacuum leak! Also, make sure the rubber intake elbow isn't torn.

[reelizmpro]

Try another idle control unit and valve. Shouldn't cost you too much.

[thebutterson]

Best thing to find a vacuum leak! Also, make sure the rubber intake elbow isn't torn.

Just looked that up, it's like $850?!

[Hey_You]

Never said it was cheap. Got one at the shop I work at, it does wonders

[ruizl300]

Hey_you, How much is it to have a shop use one of those and find the leaks for me?

[Hey_You]

Figure most shops charge by the hour to do that kind of stuff. I know my shop's rate is stupid high ($120/hr) but figure about half that at a shop that has more competition.

[318cody]

Thanks for your responses guys but as I said in the OP, there is no vacuum leak. I've had it checked by multiple mechanics who assured me the idle is not caused by a vacuum leak. I also tried a soapy water test and a smoke test, no leaks to be found what so ever. ICU is brand new. I'm gonna try another valve, even though the bmw mechanic said mine works and my car revs out of control with out it. I've been thinking it's got to be a computer or sensor that's toast somewhere. Anyone have any ideas which one's to be suspicious of?

thanks again