Hi everyone,

Driving a R56 Cooper S 2012 N18.

Currently just got a custom map with my recently built forged engine.

I’m currently having this idle fluctuation hunt and it feels like the car is gasping with a slight jerk during cold start or warm start everytime. There isn’t any fault codes and it smoothens out after it’s warm and seems to drive alright.

I have uploaded an video of the warm start, please look at the needle.

I have new plugs, coils, injectors, vanos, hpfp, lpfp literally change what could be the caused. Done pressured leak test as well.

Please help or throw me any advices, it’s bugging me

Thanks in advance!

 

Recently rebuilt... What did you do for break in procedure? How many miles since rebuild? Are you sure there aren't any vacuum leaks? From your video, the tach needle isn't moving around all that much.

 

For break in, first thousand km follow by five thousand km with oil change interval. Been about 10 thousand km as of now.

I did pressure test there and doesn’t seem to have any leak according to the test.

yes, the tach needle isn’t moving much but with the minimal fluctuation, it feels like it’s gasping.

 

With another car idle fluctuation was due to an intake air leak which turned out to be a bad air/oil separator. But with an engine that's been apart then put back together could be an intake leakanywhere. A smoke test is what a tech would do.

Before smoke test systems my auto tech buddies demo'd finding intake leaks using carb or brake cleaner in an aerosol can and with the engine idling spray at the various areas where an intake leak could be possible. This includes vacuum hoses/fittings. If the engine reacts you've hit a leak with the spray.