[trickystar]

my rpm would go up and down inbetween 500 to 900 rpm for like 20 seconds when i start up my car when its warm and then go back to stable 750 rpm

also when i have to come to a complete stop when i am on 2nd gear (the car was already reduced to a very slow speed, rpm may be at around 2k?), i engage the clutch fully and put the stick to neutral, right when i engage the clutch the rpm will drop to lower then 500, close to 400rpm, i could feel the engine shake and almost stall and it will bounce back up to 750rpm

i believe this is still some what early stage of a problem cuz i can see later on when it get worse, instead of the rpm dropping to 500ish, it will just drop all the way to 0 and the car will stall. anyone out here have any suggestion of what is the cost?

information about my car
2007 e92 n54
just bought it 2 months ago
43496 miles
spark plug changed 500 miles ago (first time ever, ex owner never changed them)
walnut blast done 1000 miles ago


with these done i should be looking at coil packs next right?
what i am thinking is the old spark plug was damaging the coil packs because they were tooooooooooo old and worn out and need way more electricity produced from coil to get the spark, that will put the coil to over heat and turn bad? not sure if my theory is right tho.. i am still pretty new at this so please help me out!!

and just in case i do have to change my coil packs
should i be looking at the oem ones or aftermarket ones like this?

http://www.vivaperformance.com/ip-co...xi-n54-engine/

[N54Fiend]

Does the car turn over right away on a cold start, or crank for a while? Also, have you gotten any reduced power codes by chance?

[trickystar]

on cold start the rpm would stay at around 1k steady and then go back down to 650~700 in a very steady speed, never jumped up and down like on warm start

and no code came up yet so far =[

any idea?

[hoopvillian]

Check vacuum hoses, might be a boost leak. Just a guess.

[fr3nch2]

Do you have a way to check for codes?

[trickystar]

i use cobb v3 to check for codes, but no code shown. about the vaccum hose, how do i check if its leaking?

[N54Fiend]

Are you using the cobb to tune the car? If you are, when you de-tune the car, are the issues as noticeable? Same problems?

[Zach335i]

You might have some bad fuel injectors. Early 2007s builds weren't included in the recall.

[trickystar]

problem was there before i installed the cobb v3 N54Fiend

i think the car's build date was at 2006 instead, but my fuel injectors are actually index 10, donno if that makes it better or no. Zach335i


and just noticed today if my A/C is off the problem seems worse.. how could this be possible to have anything to do with the drivetrain ?? so weird

[N54Fiend]

I'm with hoopvillian... could be a vacuum leak. Any hissing coming from the engine bay?

Heres a decent video of how to diagnose, but neither of those things are something I'd want to try myself. Let someone with shop insurance do it lol.

Here

At this point I'd take it to a shop and let the professionals tell you whats wrong. If you take it to BMW they usually apply the diagnosing fee towards the fix. Sometimes with something small they'll just go ahead and fix it. But dont count on that.