hi I'm new to this site,i have a 1998 xkr 4.0 with a few modifications. engine upgrades include smaller top supercharger pulley and larger bottom pulley ,I've also added larger intercooler and upgraded cooler pump ,cone air filter,stainless exhausts and free flow cats .engine was running great apart from a little hot but now as engine warms up it won't run properly,this has got worse over a short space of time first after a few miles now after a couple of minutes running . i have replaced the water temp sender unit to no effect ,i can't detect any air leaks either. i removed the air temp sender from the rear of the right hand charge cooler and checked it on a multi meter blowing hot air over the end and it seems to be working fine ,so i refitted the sensor but left it disconected this put the engine into restricted performance mode but the engine runs fine .ive used an icarsoft 930 diagnostic reader but its telling me nothing ,any ideas would be very much apreciated I've ran out of ideas .
thanx DAZ.

water pump been relaced of late, orig, no idea how old it is?

hi yes i have replaced water pump timing chains tensioners and gaskets all at same time as the pulleys and sc/cooler pump 3 months ago .

Reconnect sensor properly then watch OBD live data for all sensors you can figure out and fuel trims. Do it when all's OK and again when warm looking for what changes.

thanx jag v8 but thats the first thing i did and i got nothing off the diagnostic tool ,thats with ignition only ,wires connected ,un connected cold and warm thats why i started pulling wires off and checking sensors as best i could. I only have an icarsoft 930 which is supposed to work with a 98 xkr (car is on diagnostic menu when switched on)but all it states is no dtc's found.I don't know of any sensibly priced machine that will work with my car or a decent mobile diagnostic company in my area,and i don't fancy paying two kidneys and a lung to jaguar.

QUOTE: "thats the first thing i did and i got nothing off the diagnostic tool ,thats with ignition only ,wires connected ,un connected cold and warm" END QUOTE.

Are you driving the car with the code reader attached to view the 'live' data as it is generated? Starting the engine cold with code reader attached, then waiting for it to warm up enough to start running rough, and hopefully display some transient errors that may not be enough to trigger an actual code, only restricted performance, that is reset after stopping the car, and allowing it to cool down before restarting?

Exactly

+1 -- see my previous post

Are you getting P1111? It is supposed to be an "all OK" code. If you are not even getting this, you might want to do research on the specifics of this reader and the earlier XK8s. There are posts on this site that talk about older wiring conventions and even protocol differences.

https://www.jaguarforums.com/forum/x...nt-read-66366/

and

https://www.jaguarforums.com/forum/x...ng-ecm-140808/

Even before this, check if there is any software update I suppose.

Best of luck, keep us posted.

Do you still have the Nikasil block? If you do this could be the beginning of cylinder wash. When restarting do you experience a little difficulty getting it started?

QUOTE: "I've also added larger intercooler and upgraded cooler pump ,cone air filter,stainless exhausts and free flow cats .engine was running great apart from a little hot but now as engine warms up it won't run properly,this has got worse over a short space of time first after a few miles now after a couple of minutes running" END QUOTE.

The only other thing I could think of doing, in the absence of an actual code to direct you in your search, is to go along the ENTIRE route taken when modifying the motor looking for connectors or ground straps that may have worked their way loose, or are unplugged, although, I think unplugged would throw a code. Also, is there any way coolant could have gotten into your coil packs and plugs during the upgrades, that has slowly worked it's way down past the rubber boot to the spark plug? Did all the modifications happen at the same time i.e. exhaust system and S/C pulley upgrade, inter-cooler etc.; if not, which upgrade immediately proceeded the symptom's first occurrence? Could the new exhaust system be expanding with heat causing an air leak to an O2, or other exhaust system sensor, with expansion and contraction being the initial cause, until it got to the point where it is completely distorted and hardly sealing at all thereby causing your symptoms to occur, as you have stated from driving it for a few miles, to a few minutes until it begins running rough?