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Discussion Starter · #1 ·
So I've had a rough cold start idle since I bought my car back in January 2014. The car had 88,000 miles on it. It now has 96000 miles. I figure I inquire about this before there is any serious issue.

My car has no check engine light, EML etc. When I start it up in the morning, it has a rumble sound for about a minute after it has slightly warmed up. I believe the car is building up oil pressure???

BUT if I slightly press the throttle, the rumble goes away. I keep the RPM around 1,000 and it appears to have no odd engine rumble.
My car runs great when it's all warmed up and I believe it has all the power it should, it pulls hard with no hesitation.

The vanos has a slight clack by listening to it with a stethoscope, but I believe that is also normal and not excessive. Maybe it just needs the seals replaced or the throttle body has to be cleaned? I've got no clue. :banghead:

Anyone have similar symptoms? Please let me know what you think it could be. I've read a lot about this issue and haven't found anything quite like this on the forum. Thanks! :thumbup:
 

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What about the motor mounts? They tend to get old and stiff and squashed down. I'd noticed a bit of cold weather, low rpm "rumble" on my M3 this past winter, which I have been attributing to aging engine, and maybe tranny mounts/ bushings.

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Could be a number of things. Do you see fluctuations in the idle upon start up? Any codes or lights illuminated on the dash?
 

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Discussion Starter · #4 ·
What about the motor mounts? They tend to get old and stiff and squashed down. I'd noticed a bit of cold weather, low rpm "rumble" on my M3 this past winter, which I have been attributing to aging engine, and maybe tranny mounts/ bushings.

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The motor mounts were replaced about 10 months ago. I doubt it's that. The tranny mounts probably should be replaced but I don't think it's contributing to this particular issue.

I have no codes or service lights that come on and the car passed the DC smog/emissions test a couple months ago with no issues.

This morning i turn the car on and let it run for 10 secs. I turned it off and started the car again and the rumble was gone... All the coils are good, spark plugs were recently replaced and the car does drive very nice once it's all warmed up. Could it have anything to do with the secondary vacuum pump? Does this car have a cold start cycle it runs with the exhaust recirculation that could make this noise? I don't know where to look because the vanos actually appears to be very quite.

I'm tempted to make a video soon so y'all can hear. I wonder if a broken exhaust hub bolt could cause this?

Thanks for the valuable input. I'm just looking for really any advise or thoughts.
-Tim
 

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A broken hub tab would probably not cause an intermittent issue. It would normally either cause no problems until the second tab broke or exhibit constant symptoms. An intermittent issue is really, really unlikely. That said, some people have had two broken tabs and no issue surface. The only way to be 100% sure is to physically check it.
 

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Discussion Starter · #6 ·
A broken hub tab would probably not cause an intermittent issue. It would normally either cause no problems until the second tab broke or exhibit constant symptoms. An intermittent issue is really, really unlikely. That said, some people have had two broken tabs and no issue surface. The only way to be 100% sure is to physically check it.
I hear ya. I think what I am first going to do is replace the transmission mounts and go from there. They def need to be replaced anyways so why not start with that. It could be the slight rumble issue due to the worn bushings on the transmission but I can still bump the throttle slightly and it goes away. I still can slightly tap the throttle while the rumble is present and then it goes away.

I'll replace the transmission mounts soon and if that doesn't solve it, I will upload a video.
Thanks all for the input.
-tim
 

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If you think it's mounts, the engine mounts are known to fail more commonly than the transmission mounts. Have you checked those? Just look at how much clearance there is between the oil pan and front subframe.
 
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