Engine starts and idles but then misfire above 1500rpm.
Posted: Tue Mar 03, 2009 9:04 pm
by nortonjaguar1
Hello can any body help please; X300 95 reg 3.2 Sport 103K miles; engine will start and idle but goes into misfire, coughing through intake above 1500rpm. I had this problem about six months ago but it cleared itself overnight, then about six weeks ago it happened again. New plugs were fitted with no change but then two ignition coils were replaced and the engine ran fine. Last week I felt a slight hesitation on acclereation then after about two miles the car went into misfire again. Items now substitued include; all ignition coils replaced with new; used air flow meter and air temp sensor but fault remains. I shall try substituting ECU; throttle body and fuel pressure regulator but wondered if any body else has had the same problem and what the cure was? If I find the cure then I will update this message. Thanks for looking. Hugh.
Update on engine misfire.
Posted: Thu Mar 05, 2009 10:12 pm
by nortonjaguar1
Well I finally, after many hours sorted the problem!
The car had the MAF sensor; throttle body plus potentiometer; engine coolant temp sensor (the one with two leads on the inlet manifold); engine air temp sensor; fuel pressure regulator; engine control module; spark plugs; ignition coils; air filter all changed and the continuity of various cables checked and the engine would start immediately and run at idle but still misfire above 1500rpm. Fuel pressure tested just fine as did engine vacuum.
The car was checked for error codes and none were recorded. Eventually I decided to substitute the crank position sensor even though it is only 18 months old, hey presto problem solved. These sensors normally fail outright and prevent an engine from starting (no CPS and therefore no spark nor fuel) but it goes to show that even one that passes all static tests off the car can still be the cause of this problem.
I would also like to add thanks to Royles of Wilmslow and Dan at DC McCalls of Woodford, Stockport, if you want good service these people are helpful and can be trusted. I do declare an interest in that I have retired and I do sometimes drive for Royles (I have Advanced Driver membership for motor cycle and car).
Hugh.