Hi all, I'm having a bit of a rough idle on my Mini and I'm not sure where to start diagnosing problems. It's a 2006 Cooper S project car with 72,000 miles.The engine feels like it steadies itself out over 1000 RPM, but when dropping the RPMs after accelerating it cuts out for a second (drops to around 600rpm, doesn't sound like its firing at all, then levels itself out). When idling, it almost sounds like there's a misfire as the firing sound is rough and not very steady. Listening to the engine from the bay, the valves sound a bit noisy, but no more than any oldish car I've owned. It also takes a bit longer to start up cold than hot, but even when hot it doesn't start up as quickly and cleanly as I've seen with other R53s. Almost like it's struggling to turn over sometimes. I checked with a OBD2 scanner and the following codes came up: 1477 and 1498.

I've read around a bit and found that it could be a leaky vacuum line or an intake leak, which is backed up by code 1498. Code 1477 leads me to believe it could also be a fuel related issue.

New spark plugs and coils installed last summer when I dropped in this engine. New air filter, SC was serviced last summer. Brand new battery purchased today.

I appreciate any advice, I'm not very familiar with these cars and am using this project as a learning experience.

 

What are your long term fuel trim values?

 

A simple check for a vacuum leak is to judiciously spray starting fluid (Ether) around the usual suspected areas in the engine compartment. If the rpm's increase, you've found the leak. (Caution: Starting Fluid is extremely flammable! ...Duhhh!)

 

Soapy water in a spray bottle will do the same thing and, here's a bonus, you won't set yourself on fire!

 

Doubt you'll set yourself on fire unless, perhaps, you're smoking a cigarette and have the nozzle pointing at you. Might be a candidate for the Darwin Awards