[bsteven42]

Hello, this is my first time starting a new post so sorry if there are any errors. I've searched this forum and others at length and cannot find specifics to mine.

I have a 2007 N54 335i and started having rough idle at cold start. Instead of RPM being above 1k, it drops and fluctuates between 500 and 1000 RPM and then shows limp mode. If I turn the car off and restarts, it runs just fine. Using inpa it only throws code 29F2; no misfire codes or anything else shows up. It acts like it's not adjusting the startup idle correctly. After a few seconds the RPMs adjust to what should be the normal startup idle and everything works ok except for the limp mode light.

When it first did this and gave the 29F2 only code, I figured it was my HPFP. By carfax the car had already had the pump replaced a few years ago under warranty (someone else), but I figured it had gone out again so I purchased a new one. I installed it and it does exactly the same thing. I've done no tuning.

Other things I've done to tried:
- Changed oil (twice)
- Replaced spark plugs
- Replaced vacuum hoses
- Tightened turbo wastegate rattles
- Pulled new spark plugs, no evidence of fuel leakage from injectors, no fuel smell during startup
- New fuel rail pressure sensor
- New coolant temperature sensor

Since I'm still only getting the 29F2 code I guess it could be that I received a bad HPFP, and it does have a warranty, but I don't want to send it back and have them say there's nothing wrong with it. Especially if it's doing the exact same thing before and after.

I've read that it could be the injectors, but when I pulled the plugs they looked exactly the same: a little carbon but otherwise clean. I would think that if it was a bad injector(s), the injectors that were bad would have different carbon buildup.

Tomorrow I am going to check the HPFP and lpfp pressures to help provide info.

Thanks and help is much appreciated!

[suk610e92]

Are you able to check your low fuel pump pressures might be a failing or faulty LPFP I think inpa allows you to check LPFP PSI and HPFP PSI those values should tell you if either are failing HPFP should be at 700 at idle and LPFP should be at 70-75 at idle usually sits around 72

[bsteven42]

I checked the pressures and they looked OK, except I wasn't able to moderate the throttle. Currently if I hold the accelerator down to keep RPMs around 1K it does ok until it takes over for itself. I'm also going to try new injectors: Mine are currently only index 01. When I pulled the first spark plug there was a gas smell on it, indicating a leaking injector.

Thank you much for the response!

[bsteven42]

So I have the conclusion to my problem. I bit the bullet and took it to my dealer. They put in a new HPFP from BMW. $1800 later and the idling issue is fixed. So the "remanufactured" HPFP I put in was a piece of crap. But now I know and I have a two year warranty on the work.

Bottom line: I should have purchased an original BMW part to put in the first place.