BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Stumbling at idle and weak warm starts??

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      05-14-2012, 12:53 PM   #1
Alan l.
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Stumbling at idle and weak warm starts??

Hey guys,

My car has been acting alittle strange lately. First off i did a cold start the other day and got out of the car to wipe it down. Noticed the exhaust tone wasn't smooth like it usually is and sounds as if its sputtering a little. Got back inside the car and could feel the stumble every 5-10seconds and could see the rpm fluctuate slightly. I've always noticed the N54 doing this peridically maybe once every couple of minutes but this was more rapid. Figure the motor was cold and it go away when i warmed up. Drove around a bit until the engine was warm and the car felt normal but stumbling at idle was still there. Decided to open the car up to see how it feels and see if it would clear up on its down. Exhaust popped loud a few times after going WOT up and down the block and sure enough the stumbling went away completely. The car has been fine every since. Any ideas? Running fmic, cobb S1+, rpi exhaust with only 15K miles on the motor. 6MT

Another thing is that i'm also noticing on occasional warm starts, the engine would barely turn on. It does catch but almost sounds like it wouldn't and stall. Had my HPFP replaced last year and the car feels fine otherwise. Cold starts fires up right away too.

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      05-14-2012, 12:56 PM   #2
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Drives: 2007 335i coupe
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My rpm used to stumble at idle also. I cleaned my intake valves and that solved the problem. Since your miles are so low I would assume your valves are clean so maybe spark plugs or an injector on the fritz.

Good luck trouble shooting
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      05-14-2012, 04:57 PM   #3
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Drives: 2011 SGM 335is
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Honestly that sounds like plugs to me...on my old Jeep and my waverunners a few good WOT runs usually cleared up similar conditions, but ultimately the plugs were fouled and that was it. The job's so easy you might as well try it. Can't hurt!
2007 E92 335i - Retired
2011 E92 6MT 335is - JB4, Stett CP, Synapse BOV, Wagner FMIC, BMS OCC, CDV mod, AFE DCI, Cyba Scoops, BMS Clutch Stop, P3Cars v2.1 vent gauge, LED side markers.
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