Hello all so my 88 xk is having some idling problems and i'm starting to beat my head against the wall. So before winter i tuned it up, plug, cap, rotor, and fuel injector cleaning done. Drove it about 150 miles and parkrd it. Got it out late this summer, and is idling rough once it warms up. I have run two tanks of fuel through it, re checked the plugs, replaced wires, had all 12 injectors rebuilt, retimed it, new cap, found intake leak and fixed. I think i have checked everything ican think of. the rough idle feels like a miss but donest happen all the time, but is enough that i feel it sitting at a stop light. car has 25,500miles. Any help would be great.
Thanks Tim

Also found the plugs are black from idleing. seems tobe running rich, should note found the car will not start if coolant sensor is unpluged or will die once unplugged. omhed out at 347omhs @73degrees C.

 

Normal for engine to die/not start if CTS is unplugged.

Is 73ºC as hot as your engine gets? If so, that might enter into the problem. You need to reach about 80ºC before the system stops giving "cold enrichment".

Also check:

Fuel pressure (excessive)
Vacuum and electric enrichment switches (Stuck closed)
Pressure regulators (leaking)

Post back for details if needed

Cheers
DD

 

73C is just what it happened to be. i can wait till the electric fan turns on at full temp and still runs the same. I know that the fpr aren't leaking, by removing vacuum hoses snd turning vehicle on. Also fuel is not spraying out of them when running.
Fuel presure was good when i checked at the beginning of all this.

What vacuum and electric switches should i be looking for?

 

On the right side of the throttle capstain there is a micro switch that should only be closed at about 3/4 throttle. The wires from that switch go to a blue vacuum/elect switch a few inches away at the rear of the right inlet manifold. Make sure it isn't closed when it shouldn't be. It should close only under low vacuum.

As far fuel pressure goes I'm wondering if it's too high.



Cheers
DD

 

As above,

Maybe, perhaps someone has fiddled with the ECU fuel trim adjustment "pot" in an attempt to fix the issue prior to your ownership??. Might be worth trying to trim the idle fuel here, coz it can give a really rich idle mixture if at the wrong end of the "pot".

 

What about the 02 sensors located in the exhaust down pipes?

 

Allright now that im back from the weekend, the throttle capstain switch does not close till about 3/4 throttle.

I seem to be havinh troble finding my adapter for fuel pressure test. i'll have to keep looking.

The adjustment on the ecm hasen't been touched as i have owned the jag for a few years.

I did swap out o2 sensors from a friends 88 jag. mine runs the same but his now runs like crap with a definitely has a miss. i got some replacements on there way.

 

Update: got new o2 sensor and now she purrs like a jaguar. finally found my fuel pressure adaptor. she now has developed a hard start. the fuel pressureis about 40 psi at idle. once turned off pressure drops 10psi in 20 mins. good times.