Since I got the car (AJ16 3.0) I get a strange intermittent misfire.
The car starts well and then the revs go down and settle at around 700. That’s the time when the engine has a very little shake and if you go near the exhaust, you notice that the running isn’t smooth and the intermittent misfire.
It seems to feel smoother, but not totally, when I select D and hold the brake pedal.
The car pulls well and accelerates smoothly through the rev range and never misses a bit.
I did the following:
Battery reset procedure (when a car gets a new battery and the ecu needs to “learn”), new air filter, cleaned MAF, throttle body, and idle stepper motor (it was all filthy), changed to Champion RC12Ycc plugs, changed to new coils and used premium fuel and injector cleaning additives.
These procedures had zero effect on the idle of the engine but it still pulls well.
I’m due to replace the fuel filter soon, but the pipe from the filter to engine is corroded and I’m waiting for a new hose to replace a small section.
From experience in other cars, an intermittent misfire is usual electrical, but this one is baffling me as no lights on the dash and I don’t have a decent code reader.
I though of vacuum leak, but that would cause a consistent lumpiness.
It’s not the crankshaft position sensor either because, as pointed out by a former Jaguar engineer in another topic, it only affects the starting of the engine.
Any ideas of what else could be?
I spent already a bit on this car and to be honest, I’m ready to part with it. There other issues too and I feel that I bought a lemon.