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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Thu, Jan-26-2012, 05:44:35 AM   #1
Jtrem
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Default Idle Drop Issue..

I've spent hours reading through all kinds of threads on this exact issue. I have been suffering from this issue for almost a year now.

Issue: When releasing the clutch and going into neutral. (At a light, stopsign,ect.) The Idle drops from 900ish down to 500 then spikes right back up.

I know a ton of people have had this same issue and I find it troubling that no one has found the solution to it.

I have replaced my plugs, coil packs, Fuel Filter, MAF, ICV, Cleaned the Throttle Bodies, new pullies, new belts, checked for Vac leaks and put my stock intake back on.

Nothing. I thought the issue had went away, but then it would come back randomly.

The last thing I can think of is an issue with the fuel pump. Sometimes when I first go to crank the car over the Priming of the fuel pump is loud and doesn't sound like a normal pump priming.

My idle issue seems to smooth out once the car is fully warmed up. Which almost makes me think its the pump.

I'm at the end of my ropes for this damn issue. No codes what so ever. I dont feel like spending 350-400 on a new fuel pump for the hell of it. So unless it fails or someone has anyother ides. Ill have to live with it.
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Old Thu, Jan-26-2012, 05:51:48 AM   #2
Braymond141
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Default Re: Idle Drop Issue..

When releasing the clutch and going into neutral?

This is really just two things.

Throwout bearing is failing causing too much drag with the pressure of the disengaged clutch on it. This would typically have a noise to go with it though (not always, mine was in pieces and I had no noise).

Thrust bearings in the block are worn. When you push the clutch in, it pushes the crank forward. This would be worst case scenario and requires immediate attention (rebuild).
http://image.circletrack.com/f/92999...ford_block.jpg (not bmw)

What is your clutch history?
Have someone check for crank movement when you operate the clutch.
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Old Thu, Jan-26-2012, 05:57:23 AM   #3
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Default Re: Idle Drop Issue..

It's not the clutch I know that for a fact. It's been upgraded already.

If I rev it up the RPM's will drop without even touching or having the clutch engaged. Should have made that clear.
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Old Thu, Jan-26-2012, 06:00:02 AM   #4
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Default Re: Idle Drop Issue..

Quote:
Originally Posted by Jtrem View Post
It's not the clutch I know that for a fact. It's been upgraded already.

If I rev it up the RPM's will drop without even touching or having the clutch engaged. Should have made that clear.
That isn't even a diagnoses or what I said. There's nothing the car knows about the clutch movement to have the engine drop idle. The only thing that can cause a drop in idle is drag by which the ECU tells the ICV to open up and raise the idle.

Throwout bearing or Thrust bearings, take your pick.
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Old Thu, Jan-26-2012, 06:02:23 AM   #5
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Default Re: Idle Drop Issue..

Replaced the TOB when I did the clutch.

I'll check for crank movement tomorrow though.
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Old Thu, Jan-26-2012, 06:06:03 AM   #6
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Default Re: Idle Drop Issue..

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Originally Posted by Jtrem View Post
Replaced the TOB when I did the clutch.

I'll check for crank movement tomorrow though.
I really hope that it wouldn't be that severe. I'm also unsure how much undetectable by eye movement is too much.

Are you sure it's not your A/C cycling on/off? They will cycle frequently when low on freon. Maybe it's coincidence you're shifting into neutral at the same time?
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Old Thu, Jan-26-2012, 06:10:19 AM   #7
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Default Re: Idle Drop Issue..

A lot of others have this issue. So I Highly doubt its the Thrust bearings.

One example.
http://www.m3forum.net/m3forum/showthread.php?t=322938

These idling issues span through all e46's. Including Automatic 3 series.
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Old Thu, Jan-26-2012, 06:12:53 AM   #8
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Default Re: Idle Drop Issue..

seems to only do it when it hasnt warmed up yet.

Once its warm. Seems to vanish. Like I said I can just be idling and I will give it gas and the Idle will dip down.

Thats with not even touching the clutch.
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Old Thu, Jan-26-2012, 06:14:02 AM   #9
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Default Re: Idle Drop Issue..

Quote:
Originally Posted by Jtrem View Post
A lot of others have this issue. So I Highly doubt its the Thrust bearings.

One example.
http://www.m3forum.net/m3forum/showthread.php?t=322938

These idling issues span through all e46's. Including Automatic 3 series.
This typically happens with aftermarket intakes. My K&N did this all the time before I found the MAF screen swap fix (which totally eliminated the issue).

Is your issue at a complete stop neutral shift, or while moving?
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Old Thu, Jan-26-2012, 06:20:07 AM   #10
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Default Re: Idle Drop Issue..

Quote:
Originally Posted by Braymond141 View Post
This typically happens with aftermarket intakes. My K&N did this all the time before I found the MAF screen swap fix (which totally eliminated the issue).

Is your issue at a complete stop neutral shift, or while moving?
Here is how it usually happens.

Start my car in the morning. Let it warm up a little. Wait for the idle to go down to 900.

back out of my driveway. Then when I go to put it in first it dips down. Then when I get to the stop light at the end of my street I release the clutch and it dips again. By the time I hit the second light it doesnt do it any longer.

Just when first starting out. And mostly when going from whatever gear into neutral.


It will also do it. If im just idling cold and give it a little gas without touching the clutch.
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Discussing Idle Drop Issue.. in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)