engine running lumpy

[agards]

Message:
I recently bought a 95 4.0 xjs coupe which runs beautifully. Well it did until i cleaned the engine. I used Autoglym's version of gunk and just used a hose to wash it off. She drove perfectly that eveing and next morning on a 45 minute run. I then parked her up for a hour and when I started her up again it was like she was missing on one cylinder. Any suggestions please? What I don't understand is, if it was the engine wash, why did it run ok for a while instead of running lumpy from the start? - over to you gurus

[HerefordMark]

The fault might not be related to the engine wash - might just be coincidence. But if not, I'd put money on water getting in somewhere. I guess you, like me, have learned that sticking a hose into a Jag engine bay full of fragile electrics is not recommended! It cost me a blown starter motor.

TRy cleaning off all the HT leads, and the inside of the distributor cap. Also check the fuel injectors - on my V12 at least the electrical leads are easily dislodged and if 1 comes off it will give these symptoms. Best of luck, and let us know how you get on.

HM

[ptjs1]

I tend to agree that hosepipes in engine bays can be a dangerous game to play. On my 95 4.0, I cover up all the relays etc on the inner wing with clingfilm first. Also cover the timing sensor mounted on the front right of the cylinder bank (where the distributor used to be on earlier models).

Remember that your car doesn't have a traditional distributor and HT leads. It has separate coils for each cylinder triggered from the timing sensor. Because the coils are mounted under a relatively well-sealed cover, I suspect it isn't water in there. It will be probably be a drop of water somewhere else which has moved sometime after the wash and is now causing an electrical disturbance. I've had it happen a couple of times, but you might well find that it will just go away today as the water dries off! Good luck!

Paul
95 4.0 Convertible

[agards]

If ever you see me near my engine with a hose, shoot me. Found 3 of the spark plug chambers full of water which was obviously earthing the charge away from the plugs. Dried it all out and its made a masive improvement though she's still missing on one. Will revisit it tonight.

[agards]

replaced the plugs and she's now purring again

[Mark_B]

danger!! getting water down the spark-plug cavities had caused me a head gasket failure on my 3.6 a few years back, I was driving on 3 cyls to dry out the engine, but the thermal expansion must had been too much!