Recently starting rough idle, getting worse

After two years of providing great rides in these strange times, all of a sudden my 1989 XJ6 started acting up. At first it threw “Fueling Failure”, with a bit of engine misses, and then it grew bigger. There was a squeel, which I diagnosed as a waterpump issues, and replaced it. Used a chance to replace all the coolant hoses, did that last 15 years ago. Felt good doing it!!!

Now I have very rough idle at traffic light when engine in D, but not as much in N, but all fine at any RPM involving foot on the pedal. Replaced Oxygen sensor, but that cured nothing. Advice?

What revs does it idle at? Perhaps your idle air control valve needs a clean.

Tnx for the suggestion Gary, IAC is easy to take off, I’ll clean it tonight.


DTC logged for info. You need to read the fault.

XJ40VCM.pdf (690.7 KB)