Low idle RPM--help

nuron · 11-08-2023, 11:37 PM

Ever since doing a bunch of repairs: https://www.e90post.com/forums/showp...ostcount=22712

and also changing one ignition coil, I've been feeling a very low idle: 550RPM, which makes the car shake and feel like shit. Cold idle is normal: 8/900RPM then settles down to the weird 550RPM. The car pulls and revs strong and I can't feel anything off from a misfire standpoint. Here's what I tried:

Cleaned VANOS solenoids, tested activation and OHMs.
Unplugged each coil with engine running, and I could feel the engine sound different with each coil removal. Was trying to see if there was a dead coil with this method.
No CEL.

I remember my RPMs being 750-800RPM before all these fixes, so not sure where else to check. With the exception of the coil replacement, all my repairs shouldn't affect the idle but apparently something changed. Any ideas?

eljay · 11-09-2023, 09:58 AM

It sounds like you have a vacuum leak. Check the PCV beather hose at the back of the intake manifold.

nuron · 11-09-2023, 11:13 AM

Quote:

Originally Posted by eljay

It sounds like you have a vacuum leak. Check the PCV beather hose at the back of the intake manifold.

That was my next suspicion. Thanks for the suggestion. Will take a look.

11-08-2023, 11:37 PM	#1
nuron Private First Class 80 Rep 199 Posts Drives: '07 328i Join Date: Jul 2016 Location: Washington iTrader: (0)	Low idle RPM--help Ever since doing a bunch of repairs: https://www.e90post.com/forums/showp...ostcount=22712 and also changing one ignition coil, I've been feeling a very low idle: 550RPM, which makes the car shake and feel like shit. Cold idle is normal: 8/900RPM then settles down to the weird 550RPM. The car pulls and revs strong and I can't feel anything off from a misfire standpoint. Here's what I tried: Cleaned VANOS solenoids, tested activation and OHMs. Unplugged each coil with engine running, and I could feel the engine sound different with each coil removal. Was trying to see if there was a dead coil with this method. No CEL. I remember my RPMs being 750-800RPM before all these fixes, so not sure where else to check. With the exception of the coil replacement, all my repairs shouldn't affect the idle but apparently something changed. Any ideas?
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11-09-2023, 09:58 AM	#2
eljay Colonel 1792 Rep 2,338 Posts Drives: ///M + E91 Join Date: Jun 2010 Location: NS iTrader: (1)	It sounds like you have a vacuum leak. Check the PCV beather hose at the back of the intake manifold.
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