E46 Idling Issue

[kenyon]

Guys,

My E46 Bmw idles high and low, revving up on its own. When the car is parked up or moving the revs start to rise and fall on its own from 500 rpm to 2500 rpm, they never stay constant. Its like your on and off the accelerator all the time.

The problem is very intermitt.

Any ideas? I think it could be idle valve etc.

[zeddy3]

I had this prob on my last car 2.8 z3, although it was only apparent on cold mornings. once warmed the prob dissappeared. took it to the dealer who ran a diagnostic test who could find no fault ,sold it in the end. I thought it might be the idle control valve. sorry i can't be of any more help.

[kenyon]

I have been to BMW dealer and they have ran a engine management diagonistics tests and have nothing. They said this problem is phantom problem and is apparent on E46 engines from 1999 to 2004. They said they could replace part by part until they found the problem, but it would costs. What a load of bull****.

Its just really started last week and is very intermit especially on start up.

Thanks for your help anyway.

[blackspider]

kenyon said:

I have been to BMW dealer and they have ran a engine management diagonistics tests and have nothing. They said this problem is phantom problem and is apparent on E46 engines from 1999 to 2004. They said they could replace part by part until they found the problem, but it would costs. What a load of bull****.

Its just really started last week and is very intermit especially on start up.

Thanks for your help anyway.

What a load of crap...I have yet to have this "phantom" fault..Im thinking about it and will let you know what it might be
What engine is it?

Edited by blackspider on Saturday 24th March 23:17

[kenyon]

Its 318se - 2ltr 16v 2002. Done 60000 miles.

[jay123]

i have a similar prob... 2004 e46 with 1.8 n42 valvetronic engine...
i have taken it to the dealer and they keep saying no faults found.
with mine the problem isnt as extreme... revs fluctuate between 700 - 900 on its own accord, sometime a very faint "wobble" cant be felt through the footwell and seat also acceleration upto 2000 rpm is sometimes lacking...

it would be interesting to see what the issue is

[Vandad]

I had this issue before, there is a part of engine called : (Stepper motor) which keeps the idle constant. It might be broken OR another possibility is that the ECU has many error codes which needs to be reseted.
It worths if you take your car to someone who can read the ECU codes first.
Stepper motor would cost you about £40, make sure you tune your engine after installing the new stepper motor.

[HomerJ]

Hi,

I'm not familiar with the set up, but if it's any help I had a similar problem with a Bosch LE Jetronic system years ago which was easily cured (well, not easy enough for the dealer).

The air bypass valve, or idle valve, being down stream of where the crank ventilation fed back into the air intake, got mucky and caused the problem you described.

I used to turn it fully in, counting the turns, unscrew it and clean off what looked like very little dirt with a cloth, put it in fully and turn back what I'd counted and adjust idle. Needed doing regularly but not too onerous.

Iirc, I opened the air flow meter too, tightened the spring (having marked it, in case) and re-sealed it with silicone sealant. It wears over time but I can't remember what difference it made.

Whatever, cleaning the valve is easy and if it's not that, no harm done.

Hope it helps.