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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Mechanical Maintenance: Break-in / Oil & Fluids / Servicing / Warranty > VIDEO - unexpected acceleration in idle at start up



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      01-12-2011, 08:45 PM   #1
taxman73
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VIDEO - unexpected acceleration in idle at start up

So I recently noticed that upon starting my car, it goes to it's normal idle position, but then seems to raise and lower a little bit and suddently after a couple of seconds jumps up to about 1600/1700 rpm and slowly goes back down. It looks as if someone is pressing the peddle as you see the rpm jump up but I have no feet on any pedal while it happens. I have notified the dealer and the car is going there tomorrow.

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Any suggestions as to what it could be?

Thanks,
Greg
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      01-13-2011, 08:46 AM   #2
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Holy crap this morning was even worse. It rattled around back and forth between 500 and 1000rpm before shooting up to 1600rpm, then went back down to the normal idle.
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      01-13-2011, 12:24 PM   #3
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the 335's does that to warm up the engine, but urs seem to rev a lot higher than mine. Mine only hits the 1000 mark and slowly drops down, I don't know if revving that high is normal or not. Take it to the dealer to see what's going on.
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      01-13-2011, 02:37 PM   #4
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Dropped the car off at the dealer this afternoon. Also mentioned to them the lurching feel when at a stop sometimes with the brakes which people have had numerous threads about on the forums. Showed him the video of the weird idle. They are keeping the car overnight to see if it does the same for them in the morning. But also he pulled on the computer that my car has a recall with the computer system and that they would do an entire computer reprogramming/update of the cars who system. He was saying the weird idle may be a faulty temperature reading and too much fuel going to the engine due to it thinking its a temperature that is incorrect. So I'm happy and look forward to seeing how it comes out. The guy told me that the updating of the entire computer system can take up to half a day so I am interested to see if everything works out fine come tomorrow when I pick it up.
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      01-13-2011, 08:03 PM   #5
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Quote:
Originally Posted by taxman335xi View Post
Dropped the car off at the dealer this afternoon. Also mentioned to them the lurching feel when at a stop sometimes with the brakes which people have had numerous threads about on the forums. Showed him the video of the weird idle. They are keeping the car overnight to see if it does the same for them in the morning. But also he pulled on the computer that my car has a recall with the computer system and that they would do an entire computer reprogramming/update of the cars who system. He was saying the weird idle may be a faulty temperature reading and too much fuel going to the engine due to it thinking its a temperature that is incorrect. So I'm happy and look forward to seeing how it comes out. The guy told me that the updating of the entire computer system can take up to half a day so I am interested to see if everything works out fine come tomorrow when I pick it up.
lurching feeling = "sticky brakes"... there's a SIB for this.

as for the revs, looks like HPFP/injectors are on their way out. mine did this for a few days, then bam... all spark plugs, all injectors, HPFP and LPFP were replaced. hopefully you won't experience what I went through, but surely something is not right there. the software update won't entirely fix the issue.

good luck.
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      01-14-2011, 01:09 AM   #6
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Looks like HPFP dealing with low AFR's.
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