[lconn]

My 2008 335i just started doing the rough running with sel when the throttle is over 50% but would reset if you let off with no codes. Today it went into limp/half engine and stayed. It finally coded which I read with the jb4. JB4 only on in the last 4 months. No slow crank.

On a long shot I reset the codes twice and it started running again though presumably with the same problem as it had before. It is a CPO car and is already on it's third pump in 77k miles and the injectors have been replaced twice. Only Shell fuel, no ethanol .

I'm going to move some parts and see if the codes move but it is 3 cylinders plus a sum error. The problem with taking it to a dealer is that if it's not a hpfp problem and the injectors, coilpacks, etc are the problem, you're in for a big bill and they often troubleshoot by replacing lots of stuff when they don't actually know what it is.

Any ideas how to test a 3000psi pump or at least isolate the problem?