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Discussion Starter #1 (Edited)
My E46 325i Sport Manual now has 170K miles and ever since I've owned it (from 130K) it has had problems in the low range:

1) When the car is cold it pulls away smoothly - no problems.
2) When the car is warm, it idles smoothly with the foot off the gas at 800RPM. If I let the clutch out without goosing it - it will frequently stall and initial pull away can be jerky.
3) If I try to increase the revs (in neutral) to a steady 1100RMP the revs surge up and down between 700 and 2000 RPM.
4)In Stop-Go Traffic - e.g. on a light-controlled freeway enramp the car has a tendency to stall.

I have done the following:

1) Replaced the Mass Airflow Sensor
2) Replaced the rubber intake boots
3) Removed and cleaned the Idle Control Valve
4) Replaced the Crankcase Ventilation System
5) Replaced the DISA Valve O-Ring
6) Used an Injector cleaner
8) Replaced Fuel Pump and filter
7) Smoke tested the car - no vacuum leaks found.

Some of these these made minor differences but the problem persists.
There are NO error codes showing.

Any suggestions would be appreciated and some insight as to how reliable the idle control valve is and whether that might be the culprit.

Thanks in advance for your recommendations.
 

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40,000 miles is a long time to put up with this issue.
I gather its idling fine then stalls as you try to take off.
Is it consistent?
Is it less of a problem with the stereo turned down?
Any change in stalling behaviour when using first compared to reverse?
Does the air-conditioning compressor effect the idle more than normal? How about the power steering? Does it continue to idle reliably when you turn the steering at a standstill?
Does it sometimes stall (not idle) when you first start it?
 

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Discussion Starter #5 (Edited)
I checked fuel trims on my ODBC Reader and at 700rpm which is standing idle Short term trim fluctuates between -0.2 and -3.1. If I rev it slightly at 740RPM it varied between -0.1 and +6.

Checking the individual ST banks at 743RPM - BANK 1 peaked at +6.2% Bank 2 was +1.6%
At 700 RPM - Bank 1 +2.3% and Bank 2 -0.8%
 

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Discussion Starter #6 (Edited)
THANKS TO EVERYONE SO FAR -

Yeah 40,000 miles is a long time to put up with it but I have been slowly ruling out the likely suspects.
I found a large hole in the CCV system but replacing all of that seemed to make only a marginal difference surprisingly.
It's behaviour is reasonably predictable and consistent.
Backing up into a parking space does seem to illicit a stall almost every time. Stop-Go traffic exacerbates the problem.
The air compressor does effect it quite a bit.
It never stalls when I start it - no problems when cold.
It also idles very smoothly with foot of the gas when hot at 700RPM.
But the moment I apply the slightest amount of accelerator in neutral the revs start surging +/-300RPM at 800-1000RPM.
After about 15 seconds the fluctuating starts to even out.
 

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Have you had a look at the throttle body? On my car the TB flows a small amount of air at idle. This flow had been adjusted (I assume) reducing the flow through the TB. The ICV allowed for this by opening up more. Idle was good. Start was ok but transition to some more throttle from accelerator input was erratic. One very noticeable symptom was the idling motor stumbling as the A/C compressor kicked in. Coming off throttle the RPM would drop a bit low then lift up again. The car rarely stalled while idling but did when moving off. Hot or cold made little difference. With care the car could be got moving with no throttle. Sometimes (say 1 in 10) when cold starting it would stall when I let the key go. Next try it was normally fine.

The VANOS is another candidate. This could vary with temperature as oil thins and clearances change. This would be erratic. Sometimes drive off ok other times stall.
VANOS is a problem all E46's 6 cylinders will suffer from. BMW used the wrong material in the VANOS sealing rings. To make matters worse BMW do not supply the dodgy seals as a spare part separate from the complete VANOS. Buying a new VANOS assembly from BMW is an expensive way to renew a few dollars worth of seals.
Have a read here all is explained.

I hope this helps.
 

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I no longer have the stalling problem at all. I changed both camshaft position sensors with bmw ones purchased from Bethpage.com and replaced the lower intake boot purchased in the cold climate upgrade pcv/intake kit from fcpeuro.

Sent from BimmerApp mobile app
 

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Discussion Starter #11 (Edited)
Ok, thanks for all your suggestions. I replaced the idle control valve and the two intake boots as an added precaution and the stalling problem is pretty much gone.

Transition from idle to higher revs is not as smooth as it should be but way better than what it was.

I guess the Vanos seals should be the next project.
 
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