Idle fluctuation issue :going insane:

[8920vt]

http://www.youtube.com/watch?v=Vjy-s...e_gdata_player

I ran across this video and at the end of this video is exactly what my car does. It drives me crazy and I can't seem to figure it out. I've been searching for forever

My m50b25 vanos has no vacuum leaks. It's been smoke tested at 13 psi and didn't leak a bit. The vanos is new, cam sensor is new, maf is new, o2 is new, icv is good tps is good, no cel

Please help. This thing is driving me nuts.

Thanks
Ian

[RobertK]

How new is the ICV?

A friend of mine had a similar issue. He went through replacing everything except the ICV and then when he finally replaced the ICV it stopped.

[hwy84]

Unplug ICV connector. Start the car. Still do it? I bet not. Should idle smooth at about 1,100 rpm.

Turn off the car.

Plug the ICV back in, and start the car again. Idle will fluctuate from about 500-2,000 rpm for about 30 seconds, then should settle in. If it doesn't settle in, your ICV is bad.

[greyis89]

This would have been helpful when I was diagnosing a similar problem. Put a new icv in and no change and later found it was the maf sensor that was bad.

[SwiftE30]

i had this exact same problem. My ICV was bad/really clogged up inside. do what hwy84 said.

[8920vt]

Thank you for the suggestion but it didn't work the icv is good. And with it unplugged it still did that fluctuation.

Tried a new crank sensor and that didn't do it and 3 other ecus and it hasn't changed

Any other suggestions?

I'm ready to burn this thing.

Thank you for any and all help

Thanks
Ian

[AnimalE30]

Originally Posted by 8920vt

Thank you for the suggestion but it didn't work the icv is good. And with it unplugged it still did that fluctuation.

Tried a new crank sensor and that didn't do it and 3 other ecus and it hasn't changed

Any other suggestions?

I'm ready to burn this thing.

Thank you for any and all help

Thanks
Ian

From what rpm to what rpm is it fluctuating? The problem in the video is part throttle fluctuation, not idle.

Is your issue more like the engine is fluctuating because it's trying to keep itself from stalling?

[hwy84]

Originally Posted by 8920vt

Thank you for the suggestion but it didn't work the icv is good. And with it unplugged it still did that fluctuation.

Tried a new crank sensor and that didn't do it and 3 other ecus and it hasn't changed

Any other suggestions?

I'm ready to burn this thing.

Thank you for any and all help

Thanks
Ian

That's good data. Now do the same excercise, but instead of disconnecting the ICV, disconnect the MAF. Any change?

[edit] I see that you said the MAF is new...

The fact that disocnnecting the ICV has no affect leads me to think that your ECU isn't aware that you are idling, and not at part throttle.

Are you sure that your throttle plate is adjusted all the way closed at idle? And are you sure your new TPS is adjusted correctly as well? It needs to tell the ECU that you are idling, at part throttle, or at WOT.

No codes?

[8920vt]

No codes, also forgot to mention I've tried 4 known good throttle bodies, the maf is good checked the new one too. And I've tried three ecus

The throttle plate is closed

I have no idea what this could be. I'm going insane.

And yes this is a fluctuation off idle it's generally between two to three thousand rpm and it just seems to cut off but a second later it pics right back up. But you can easily replicated it by holding the throttle open at 3k and not move throttle position then it starts to do that fluctuation like in the end of the video

No codes
The fuel pump is new
No vapor lock issues
Runs perfectly fine beating the piss out of it throughout the rpm range, but it does this while cruising and at lower loads on the motor

Thanks again.
Ian

[8920vt]

Sorted this. Way back deep in the harness there was a broken wire in the wiring to the throttle pos sensor.
Thank you so much for all your help!
Ian