So basically over the last few months i've been feeling like my car isn't running right but don't really know what's wrong. It's a 2009 335xi with around 54k miles on it right now and no warranty. It's basically a combination of things that have been getting me worried and instead of throwing parts at it I wanted to see if anyone here has had similar issues and can provide help.
The first issue and maybe easiest to fix is a rough idle. When i'm sitting in a lot for a while with the car idling at operating temps i'll notice an occasional vibration or unsteadiness to the idle. I'm assuming this might be able to be fixed with a walnut blasting but don't really know?
The next issue i'm having is a noise which started a few months ago over the summer. During the summer basically if I gave the car light throttle in neutral and kept it under 1k it would produce a squeaking noise. That went away a few weeks after so I ignored it but now i'm having another squeak every time I shut off the car... I read someone on here had a squeaking issue too and it was the clamps on the downpipes being cracked or broken. Is that a possibility? The other thing i'm thinking is maybe the crankshaft pulley and or belt needs to be replaced? If that's the case my main question is should I go aftermarket or stick to oem? I know NST has their lightweight pulley and ECS has their "quick spool" pulley but don't really know if they have gains. I was also reading about them getting rid of acoustics, harmonics (or something like that) which the oem one has but don't really know much about this... Can anyone elaborate?
The last issue i've been having is what feels like very subtle misfires. I had the spark plugs replaced at 48k miles and then got some bad misfires around 52-53k miles and it wound up being the cyl 3 injector so I replaced that and had it coded in. Basically if I go into any of the higher gears and floor it from a low RPM the car just sounds awful. The best way to describe it is a sort of droning sound and the car starts to vibrate slightly. It doesn't really feel like a misfire but I don't know what else could cause that... Today I was also doing a quick 3rd gear pull and the car sort of stuttered a tiny bit like a misfire but no codes or anything of that sort.
I was basically just assuming all this stuff came with the territory of a high mileage car over the last few weeks but today decided I should probably look into them. I've done a few pulls with friends cars who I think I should've beat by a lot more than I have so I really don't think it's running as it should... Either way any help or insight on any of these issues would be greatly appreciated.
Thread I made over the summer about that noise (has a video with that squeaking noise when reving up to 1):
http://www.e90post.com/forums/showthread.php?t=760590
Video from recently. You can hear the noise towards the end after the car shuts off. It's a high pitched squeak and happens pretty much every time I shut the car off.
Edit: Forgot another issue i've been having although its more related to the tune and not the car running incorrectly. Basically occasionally during a third gear pull i'll get a SES light and then the car won't boost over 5 PSI. Once its restarted everything is fine though. The one time I turned off autoclear the 2 out of the ordinary codes I got were "29E1 Fuel mixture control 2" and "2D2E angle of throttle valve * intake pipe underpressure. Correlation" I also looked at some logs from early december and noticed the car was overboosting the target at some points. Could this be whats causing this? Anything to worry about or is this maybe just an issue since its so cold?