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Discussion Starter #1 (Edited)
Hi! I just joined this forum because I have an BMW e46 325ci that has something faulty with the engine. When the car gets somewhat warm the idle will start "jumping". It goes from high RPM and drops quick to low RPM, then catches up again and rises RPM. Most of the times this jumping will stabilize and stay at around 800. But sometimes it increases it's swings until it goes so low that the engine stalls. The car is also sometimes very weak on low RPM so when I start on 1;st it dies. I have done an VANOS rebuild which helped a little bit because it's somewhat stronger on low RPM, but the same problem still exists. I have checked DISA valve and it's fine. Also can't find any vaccum leaks but haven't looked to much. Still problem still exists even when I disconnect MAF. No warning light in instrument panel!

Does anyone have a clue to what it could be? Thanks in advance!
//Benjamin
 

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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616
I have read that. I thought about what they said about secondary airpump. Because I don't have on in my car... I have the mounts for the airpump but I do not have the airpump itself. What is the secondary airpump used for and should I have one? The car did'nt have one when i bought it.
 

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The secondary air pump (SAP) sends air into the exhaust manifold when the engine computer (DME) is running in the open loop mode. What is the open loop mode? Its called open loop because the DME isn’t using the data from the pre-cat O2 sensors. This mode is an overly rich fuel/air mix that used by the DME for up to 90 seconds after a cool start. This is done to a) get the engine up to operating temperature quickly, and b) get the catalytic converters hot enough so they are properly working. The DME senses the coolant temp (via a sensor in the cylinder head). Once the coolant temp reaches a specific temp the DME reverts to the closed loop mode. This is the normal mode of operation.
 

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Discussion Starter #5
The secondary air pump (SAP) sends air into the exhaust manifold when the engine computer (DME) is running in the open loop mode. What is the open loop mode? Its called open loop because the DME isn’t using the data from the pre-cat O2 sensors. This mode is an overly rich fuel/air mix that used by the DME for up to 90 seconds after a cool start. This is done to a) get the engine up to operating temperature quickly, and b) get the catalytic converters hot enough so they are properly working. The DME senses the coolant temp (via a sensor in the cylinder head). Once the coolant temp reaches a specific temp the DME reverts to the closed loop mode. This is the normal mode of operation.
Okay, but I don\t have the SAP. Could this be why my car is running poorly? Or should it work without it?
 

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SAP is really to burn the extra fuel in the exhaust stream to help warm up the Pre-cat O2 sensors and the catalyst quicker.

This has not major influence or bearing on the initial cold start performance.

Stalling tends to be a function of Lean conditions due to air leaks and/or a ICV that is not functioning properly.
 

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Have a look at the ISC.
...or, as I was going to say, the idle control valve.

Mine did the same thing. I cleaned the ICV--remove and spray out from all different direction with throttle body cleaner until you hear the valve clink 'brightly.'

Turn it in all directions...spray up, down, sideways. I used a can and a half...probably overkill...but I didn't want to have to do it again for a long time. It's been, probably, 10 years now. :)

I also cleaned the throttle body while I was there anyway.

...and if it's not this, then it might just be a torn lower intake boot. You should replace that anyway if you haven't. If you see a major tear in the elbow of it, it's probably 'just' that so you don't then have to futz with the ICV.
 

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...or, as I was going to say, the idle control valve.

Mine did the same thing. I cleaned the ICV--remove and spray out from all different direction with throttle body cleaner until you hear the valve clink 'brightly.'

Turn it in all directions...spray up, down, sideways. I used a can and a half...probably overkill...but I didn't want to have to do it again for a long time. It's been, probably, 10 years now. :)

I also cleaned the throttle body while I was there anyway.

...and if it's not this, then it might just be a torn lower intake boot. You should replace that anyway if you haven't. If you see a major tear in the elbow of it, it's probably 'just' that so you don't then have to futz with the ICV.
Thanks! Will have a look at the lower intake boot tomorow and clean the ICV while I'm at it. Tell you how it go
 

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All the rubber hoses, i.e. vacuum lines, o-ring, upper intake boot, lower intake boot, o-rings, CCV, in all BMW, in this case E46, will need to be replaced in order to resolve current air leak, as well as future air leak. Cleaning of ICV, secondary air pump, DISA, are highly recommended.

Your 1st priority is to identify the air leakage, then perform those preventive maintenance. This will ensure your engine is going to run free of air leak/vacuum related problems, which can easily 1-3 times per year, if you ignore it
 

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Discussion Starter #11
...or, as I was going to say, the idle control valve.

Mine did the same thing. I cleaned the ICV--remove and spray out from all different direction with throttle body cleaner until you hear the valve clink 'brightly.'

Turn it in all directions...spray up, down, sideways. I used a can and a half...probably overkill...but I didn't want to have to do it again for a long time. It's been, probably, 10 years now. :)

I also cleaned the throttle body while I was there anyway.

...and if it's not this, then it might just be a torn lower intake boot. You should replace that anyway if you haven't. If you see a major tear in the elbow of it, it's probably 'just' that so you don't then have to futz with the ICV.
Today I checked my lower intake boot and ICV. They were both fine... No carbon build up and also the intake boot looked like it had already been replaced, it was so fresh. So now again I don't know what to do... Although I found out something interesting. If I have the car on idle it runs fine. But when I turn on the headlights or AC, something that draws alot of power, then the idle starts going up and down. But it can also happen when I come from driving to a stop. I got a tip that it could be bad battery but I tried charging and also connecting double battery and it didn't solve it :(
 

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Make sure you oil the icv after cleaning. It has to move very very freely. If there is any resistance to movement it will cause surging idle and stalling. I just used synthetic motor oil. My car stalled 10 times in one day and the icv looked ok and would click when you shook it hard enough but it should click with very little shaking.


Sent from my iPhone using E46Fanatics
 

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OP...on the iCV...I removed mine and cleaned it with a can and a half of throttle body cleaner...from every angle I could think of. When you clean it, you should hear a bright clicking of the valve...not a dull hit. I'm not sure if you'd cleaned it at all...but if not, it's worth the bother to remove and clean.

Fixed my surging idle and haven't had to return in nearly 10 years to clean it...Techron ftw!
 
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