Low/lumpy idle and jerky acceleration

Post Sat May 16, 2015 9:15 am

Got my M52B25 swap back yesterday and I'm super excited, but there is an issue preventing me from using it.

It idles really low and lumpy and actually cut out entirely earlier. Trying to get it to rev and pull away results in a really jerky throttle response, but it smooths out above around 30mph. The car just jumps around all over the place until then. There is also a slight whistling noise, I think from the engine bay.

I'm thinking one of a few things: MAF sensor, idle control valve, vacuum leak or fuel tank condensation. What do we think? I popped half a tank of premium fuel in it and have driven about 20 miles with it, but it probably doesn't help that the engine and gearbox have been sat doing nothing for months now so I guess it will need running in.

Post Sat May 16, 2015 10:16 am

I've just been reminded that I'm still using the 328i ECU from my original plan, despite now using a 323i engine. That must be my issue! Feel so stupid.