Rough idle until engine is up to temp - Ambient air temp doesn't matter

[ChristopherL]

Hello Group,

I just completed swapping a new (used) M44 engine into my '98 318i.
Seems this is the best place to go for M44 questions.

The car has a "lumpy" idle and "stumbles" coming off idle when the engine is cold. As soon as the engine is up to full temperature, the idle is perfect and it accelerates/revs perfectly. Before the car gets to full temp, it bogs/hesitates/stumbles when accelerating or reving while standing still.

This issue is present regardless of ambient air temp. For example it was there today with 70* ambient air temps.

I have not yet tried to pull any fault codes, but there is no Check Engine light on.

It appeared all the other rough idle topics pertained specifically to when the air temps were much colder.

Has anyone run into this issue before?

Thanks,
Chris

[ChristopherL]

Additional info I should include:

• Fuel in tank is 8+ months old. I've added Dry Gas to try and offset any separation of the fuel as much as possible.
• I have not swapped or replaced the engine temp sensor
• The car has a brand new head gasket
• New intake manifold gaskets (Cyl head to manifold)
• New intake gaskets (between top and bottom manifold sections)
• Battery has been drained numerous times (to just below req'd voltage to start) during engine swap, and has not had consistent extended runs yet to fully recharge.

As soon as the car gets to full operating temp, it is 100% perfect.

I have not yet pulled codes or hooked it up up to the GT1 to find out if there are other stored codes.

[jca]

First thing I would do is check the plugs.

[teen ti]

Originally Posted by jca

First thing I would do is check the plugs.

+1

my car was running pretty rough a little while ago and i thought for sure i was misfiring and had a vacuum hose leak, changed the plugs and everything was fine

[ChristopherL]

Being new to this motor, do you prefer the Bosch FR7LDC plugs or the FGR7DQP?

FR7LDC = 2 prong
FGR7DQP = 4 prong

Thank you for the feedback,
-Chris

[jca]

Originally Posted by ChristopherL

Being new to this motor, do you prefer the Bosch FR7LDC plugs or the FGR7DQP?

FR7LDC = 2 prong
FGR7DQP = 4 prong

Thank you for the feedback,
-Chris

I run the basic Bosch copper core, two prong plugs. Experienced BMW mechanics will tell you these engines run best on the basic plug, which makes fancy plugs a waste of money. If plugs don't fix the problem, I would investigate the idle control valve. It may need replacement or cleaning.

[ChristopherL]

Originally Posted by jca

I run the basic Bosch copper core, two prong plugs. Experienced BMW mechanics will tell you these engines run best on the basic plug, which makes fancy plugs a waste of money. If plugs don't fix the problem, I would investigate the idle control valve. It may need replacement or cleaning.

Does the ICV get turned off once the car is at full operating temp?

Thank you,
Chris

[Den]

Originally Posted by ChristopherL

Additional info I should include:

• Fuel in tank is 8+ months old. I've added Dry Gas to try and offset any separation of the fuel as much as possible. . .

I wouldn't bother trying to fix anything until you try fresh gas.

As for plugs, I run the 2-prong NGK's, OE for the M42, not sure about the M44.

[zoner]

Bosch FR7LDC or NGK BKR6EK. I've used both; they're both good plugs and both work fine. Go with whatever is cheaper and/or available in your area. Anything more (4-prong, platinum, iridium, etc.) is unnecessary and probably a waste of money if your change your plugs regularly.

Originally Posted by ChristopherL

Does the ICV get turned off once the car is at full operating temp?

Thank you,
Chris

Throttle position, not engine temp., is what controls the ICV function. Signs of a bad or dirty ICV include a high-pitched whistling sound at idle that goes away about at about 1500-2000+ RPM (a bad CCV or air pump can make similar sounds) or an oscillating RPM at idle that may or may not eventually smooth out.