Hi folks I have an odd start up problem from cold that seems to come and go. The car doesn't throw up any fault codes that my Cobb AP can find, but the startup seems pretty awful to me.
Firstly the car revs very high, nearly 2000rpm, then it suddenly drops very quickly to around 1000rpm and lower, then finally rectified itself to just over 1000rpm where it usually sits on initial cold start up.
It's doing it often enough at the moment that I managed to film it on my phone whilst leaving work this evening:
The car is a 2009 135i, N54 with around 45k miles on the clock. Mods are Cobb stage 2, AR Design catless DPs and BMWP axle back. I also had some sports cats fitted into some N55 mids to sit in between.
FMIC, air filter, etc is all standard and the car always runs on premium Shell fuel.
Any ideas what the issue could be? With a start like that I'm surprised no codes are being thrown.
Once the car is started it runs fine, except at idle it shudders slightly, and occasionally gives a more violent shudder.
HPFP was changed in 2009 and so were the injectors, which now all have the "good" model number on them. Spark plugs were done approx 10k miles ago or less and oil/filter etc done a couple of weeks ago.
Help!