What would cause a M50B25 (Vanos) to run rich?
I have a lambda fitted and presumably working. Check engine light is wired up, comes on with ignition and goes out when engine is running. Comes on if MAF disconnected. Engine runs fine but only gets about 28mpg, even on the motorway. Seems constrained at low revs but takes off at around 3500.
I'm starting to get occasional misfires, but I've a feeling the CAT is now partially blocked, but I think this is a symptom rather than the cause. I'm gonna try and knock out the guts this weekend, the car is 1991 so should still pass MOT, except if it's still running rich.
I was thinking possibly coolant temp sensor, intake air temp, MAF, what else?
I know it's a pretty open-ended question, but I was wondering if there was a common cause for this behaviour.
Thanks in advance
Jon
