BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Rough Cold Start and Idle (Logs Attached)

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      07-30-2023, 08:16 AM   #1
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Drives: 2007 E92 335i
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Rough Cold Start and Idle (Logs Attached)

First post, I usually look through existing threads to find answers (I know there are already a lot of posts about this) but I've decided it would probably be easier to just start my own.

Car Details:
N54 335i 6AT flashed with MHD Stage 1+ (98RON) and xHP Stage 3
54k Miles
Index 12 injectors installed less that 5k miles ago with new spark plugs
Water pump and T Stat replaced 7k miles ago
Vanos solenoids cleaned 5k miles ago

Known Issues:
Leaking valve cover / gasket (replacement valve cover on order)
Diverter valve leak? Oil seeping onto charge pipe (charge pipe and BOV on order)
Wastegate rattle

Basically when cold starting the car it runs really rough. There are no long cranks or anything, the car turns over immendiately. Once the rpms rise and slowing drop to idle (needle does not bounce up and down) you car feel the car shake as the needle moves, the worst being when the needle drops to idle. Then it continues at idle, the best I can describe it is a rythmic thud you can feel in the drivers seat. Outside of the car you can also kind of hear it through the exhaust, almost like the car is missing but I don't have misfiring codes. This behaviour mostly stops once the car is warm but when stopped at traffic lights you can still feel it ever so slightly.

The first and only thing I've done so far to remedy is install and code brand new index 12 injectors. When I pulled my spark plugs 3 out of 6 were wet with fuel. So I went ahead and replaced them thinking that was going to be the solution. However the problem is still present. I've recently checked my plugs to make sure the new injectors haven't failed and they were all bone dry so I don't think the injectors are faulty.

Everything I read points to injectors, HPFP, LPFP etc. I did think maybe HPFP as I'm not sure if it's ever been replaced with the car being fairly low mileage. I've done some logs of a cold start and a 3rd gear pull and to me (with my very limited understanding) everything seems fine. But please correct me if I'm wrong.

I've had this issue for almost a year now and just learned to live with it as I've not had the time or money time to sort. Now I'm at the point where I want to get it sorted and start working on / enjoying the car again. At the moment I have a new valve cover, charge pipe with BOV and other various maintenance / upgrade parts on order. I'm also looking at getting the intake valves cleaned as they have never been done.

Cold Start Log:

3rd Gear Pull Log:

Any input or help would be greatly appreciated. If I've missed something please let me know.

Thank you
Appreciate 0


cold start, idle, n54, rough cold start, rough idle

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