Rough idle and vibration under braking

mmret · 08-14-2011, 03:11 PM

Hey all, could use some help with diagnosing a few issues:

Car is a 07 Z4 3.0si Roadster, all stock except for aftermarket wheels.

First issue:
Lately have been noticing a vibration felt in the steering wheel while braking from say 60km/h and up. Don't feel anything in the brake pedals so I don't think its the rotors but I could be wrong. Sound like FCABs?

Second issue:
On occasion, there will be a bit of a rough or lumpy idle. Nothing horrendous, just a subtle drop in RPMs every so often and a but of a "bump" that you can feel in the seat.

Third issue:
Maybe linked to #2. On startup sometimes the car will "rev" itself. Like if the revs are settling down to around 1k, it will "pulse" up to 1300 and back to 1000 several times in rapid succession. I think it happens more when its cold but not 100% sure. Bizzare, almost sounds like its programmed but I've never seen another car do this.

Any help appreciated.

BruceJ · 08-14-2011, 06:43 PM

If you have some mileage on them the the FCAB's are the first place I 'd look for the vibration issue.
I had the same issue on my 330i. It had approx 62K miles and was kinda loose on the steering (at highway speeds) in addition. FCAB's, new A-arms, and the steering rag joint and things got tight.

For the other issues, presuming you have some miles I would be looking at the air intake plumbing and the CCV plumbing.
First look for rips/tears in the intake plumbing after the MAF(engine hates unregistered air and idles/runs like $%^&).

Then the DISA & IAC valve. See http://forum.e46fanatics.com/showthr...highlight=disa from E46 fanatics. Great thing about your car is its most likely got the same engine that went in the E46's.

Last, I'd start inspecting all the CCV plumbling for breaks and then the actual valve.

Good Luck

08-14-2011, 03:11 PM	#1
mmret New Member 0 Rep 14 Posts Drives: 07 Z4 3.0si Join Date: Sep 2010 Location: Toronto iTrader: (0)	Rough idle and vibration under braking Hey all, could use some help with diagnosing a few issues: Car is a 07 Z4 3.0si Roadster, all stock except for aftermarket wheels. First issue: Lately have been noticing a vibration felt in the steering wheel while braking from say 60km/h and up. Don't feel anything in the brake pedals so I don't think its the rotors but I could be wrong. Sound like FCABs? Second issue: On occasion, there will be a bit of a rough or lumpy idle. Nothing horrendous, just a subtle drop in RPMs every so often and a but of a "bump" that you can feel in the seat. Third issue: Maybe linked to #2. On startup sometimes the car will "rev" itself. Like if the revs are settling down to around 1k, it will "pulse" up to 1300 and back to 1000 several times in rapid succession. I think it happens more when its cold but not 100% sure. Bizzare, almost sounds like its programmed but I've never seen another car do this. Any help appreciated.
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08-14-2011, 06:43 PM	#2
BruceJ 6 of Diamonds (ret) 82 Rep 566 Posts Drives: 2011 E93 335is Join Date: Feb 2010 Location: Georgia iTrader: (2)	If you have some mileage on them the the FCAB's are the first place I 'd look for the vibration issue. I had the same issue on my 330i. It had approx 62K miles and was kinda loose on the steering (at highway speeds) in addition. FCAB's, new A-arms, and the steering rag joint and things got tight. For the other issues, presuming you have some miles I would be looking at the air intake plumbing and the CCV plumbing. First look for rips/tears in the intake plumbing after the MAF(engine hates unregistered air and idles/runs like $%^&). Then the DISA & IAC valve. See http://forum.e46fanatics.com/showthr...highlight=disa from E46 fanatics. Great thing about your car is its most likely got the same engine that went in the E46's. Last, I'd start inspecting all the CCV plumbling for breaks and then the actual valve. Good Luck __________________ 2007 Z4Si(gone) Couple E30 Verts (DD) 2003 330i 2011 E93 335is - current fav Last edited by BruceJ; 08-14-2011 at 06:57 PM..
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