I've been having some trouble bringing the idle down on my 95 4.0 XJS. I cleaned the throttle body and replaced the idle control module and that seems to have made some difference. I think I am going to have to replace the MAP sensor as well. In addition, the car will not actively decelerate when you remove throttle. If traveling at 45 or 55 and you remove your foot, the car will coast along for some time before starting a very slow deceleration. Any thoughts?

 

You may need to find a jaguar specialist that has the PDU to reset your parameters.

Is the gas pedal sticking at all when you lightly tap on the gas pedal?

Where are you located?

 

I'll have to check that sticking throttle. It doesn't stick when I am under the hood. I am about 30 miles east of Columbus, OH.

 

You should notice whether the pedal moves effortlessly from rest of whether it "snaps" when you first press on it, then moves regularly.

I've had issues with sticky throttles in the past.

Can you also tell me what happens if you shift into neutral? While driving? Do the RPM fall quicker, stay the same, or go up? I'd prefer if you did this while you were experiencing the no-deceleration issue.

Does it do anything different if you shift into neutral while stopped at a light?

 

My 1990 had an air flow valve issue that caused a very similar problem, fwiw. The throttle was "sticky" also, but the air flow valve was the big culprit. Major PITA, too, since new ones are not to be found and the used replacement needed some machining to work optimally.

 

I think you have to calibrate the idle control valve after installing it--did you do that?
Also pretty sure the AJ6/16 has a MAF, not a MAP.

 

ok, the throttle is not sticking. I replaced the idle control valve because it wanted to idle and 1400 and above. What is happening is that is still wants to idle at that speed, so dependent on what gear the transmission is in, the car just doesn't want to slow down. I found that a short rap of the throttle will drop the idle back to ~600rpm and more normal operation. It wouldn't do that before replacement. It seems the more I drive it, the less attention I have to pay to that throttle "rap" and the car operates normally. Maybe it is learning?

Yes, MAF not MAP.. got confused with the volvo..

 

Seems to be a problem with late 4.0s. My'96 is missing at idle and will just quit if I let it idle more than 60 seconds without blipping the throttle. I cleaned the throttle valve as I was advised to do by a mechanic but there is no 'wire' in the MAF to clean. My next stop is with a Jaguar specialist near me. I will advise when I get it fixed.
RagJag

 

1199greg,

Curious if you ever resolved this issue. I have the same problem with a 1993 4L.