I've had a new problem, and possible a serious safety issue. I started my 1995 XJR as usual, put it in drive and idled out of the driveway. When I reached the street and pushed on the accelerator, absolutely nothing happened. I put the car in neutral and tried pushing on the accelerator and had no result. The car stayed at idle speed no matter what I did.

I turned the car off, waited a few seconds and started it again. It started just fine. When I pushed on the accelerator, nothing. I stayed at idle just as before.

I put the car back in drive and proceeded at an idleing speed around the block to get back into the garage. At the third stoplight, the accelerator suddenly started to respond normally and drove fine. I drove it to the repair shop and left it.

Any ideas? I've never had anything like this happen on any car I've ever owned.

 

Is there a throttle cable between pedal and throttle butterfly, or is it 'fly-by-wire' ? I had something similar with a 1980 XJ6 with "steam-powered" Lucas-Bosch L-Jetronic fuel injection. I never found anyting wrong, but a fuel injection specialist soon sorted it out, but would never tell me what he had done. Wanted to be sure of his business, I suppose.

 

Might be a problem with the traction control.

The throttle cable goes from the pedal to the traction control unit. From the traction control unit a second cable goes to the actual throttle butterfly.

When the problem occurs does the throttle pedal feel different? Unusually high or low effort to operate it?

Cheers
DD

 

Yes, there was a physical resistance to moving the gas pedal. It was hard to push, but it did move.

Any ideas what is the most common problem with traction control? Is it the electronic unit or sensors that fail?

I'd like to get my car back on the road. It is such a great car to drive!

 

This might be a longshot but you could try cleaning out the throttle body. You might have a buildup that is causing the butterfly to stick in the closed position. In some cases I've heard of the cable snapping. Also, you could try adjusting the cable so the butterfly doesn't close all the way. This is just a crude workaround though.

Mike

 

If the throttle butterfly opens OK as you press the pedal, then it indicates to me that the Mass Air Flow sensor is not detecting the increase in air flow, and thus not passing on its signal to the ECU, essentially starving the engine of fuel.

 

i had exactly the same thing happen to my xjr. it did it 2 seperate times. the first time it happened it was the throttle body sticking. jag quoted me $1600 to fix it.....i got underneath it and kept spraying the throttle shaft with "deep creep" penetrant and then some light oil and cycling the throttle plate...also made and nozzle to go into it from the inside and sprayed more penetrant onto it that way. took me a couple of hours, but it freed it up and has worked fine until the traction control system went bonkers this winter. i turned off trac cont and it allows it to work normally. since the weather warmed up, it has behaved itself....not sure 3why

 

its very common on this x300 for the throttle body to get gunked up and get stuck (esp in cold weather.). many people have reported taking them off and cleaning them to fix the problem. mine has the same problem but only every once in a while and if i give the pettle a push it fixes it self so i havent tryed cleaning mine.

 

Common, yes. The more common symptom is a persistant high idle rather than a dead throttle pedal.

I *think* the problem...on the XJR/6, at least....is the way the crankcase breather system is designed. Apparently the design lends itself to more-than-usual dumping of crankcase vapors into the throttle body. Eventually the oily deposits from the vapors build up and congeal, causing the sticking.

In fairness, dirty throttle bodies cause problems in many different brands of cars but the X300 seems to be unusually troublesome.

Cheers
DD

 

The TC unit on these cars works by mechanically pulling the throttle cable to close the throttle. When it's activated you can actually feel the throttle pedal being pushed back against your foot. If you happen to be on a zero-traction surface, like a sheet of ice, you can push the pedal till your blue in the face and the engine won't repsond...and you'll feel the resistance in the pedal.

So, anyhow, a fault in the system could have the control unit "thinking" you have zero traction....or there might be a mechanical problem with the motor that pulls the throttle cables...or the cables themselves. Turning the system off might be a good experiment...although that won't address a mechanical problem with the motor or cables, of course.

Throttle body problems are much more common, though.

Cheers
DD

 

I had the throttle body cleaned - the mechanic said it was only slightly dirty, but they removed and cleaned it anyway because I wanted it done.
The problem with the resistance to the pedal moving is still happening while driving at speed. I think I'll try driving with the traction control turned off to see if that makes a difference.
I have not had the problem of staying at idle since the one incident.

If turning off the traction control makes the pedal resistance go away, I will assume it is the TC system that is at fault. How do I go about a permanent fix? Are there sensors to be replaced? Replace the TC module under the hood? Any knowledge imparted by the experts is greatly appreciated.

 

The wheel speed sensors can be checked and I'm sure there must be some diagnostic trouble trees for the system, as well as stored trouble codes for certain faults. I've never "been there, done that yet" on my XJR so I'm not on solid ground as far as that goes.

Did the mechanic check for any binding in the throttle cables? Or any physical resistance in the operation of the TC unit with repsect to the cables going in and out? There's always a possibilty that the problem is mechanical, not electrical

Cheers
DD

 

Ok... I literally just finished fixing this problem on my car. If you can... grab the part of the TB that opens the butterfly. It is the thing that your throttle cable is connected to. Try to spin it by hand. If there is even the slightest bit of resistance then it was either not cleaned properly or there is corrosion in there. I think it can be cleaned but I actually had a spare TB that I threw on my car.
This specific problem is quite disturbing as we have those flimsy plastic gas pedals that I thought I was going to snap off!

 

I have same problem.. my acceleration is not responding and my idle is high.
i change the throttle body and problem still the same.. may i ask what is TB?
thanks plus where do i locate the throttle cable? thanks!!!

 

Hi guys, thanks for having me. Mine has the same issue. My 2003 x-type was jerking and i changed the fuel pump but it still did jerk. So the mechanic decided to clean the throttle body. Right after, the accelerator failed to respond and the idle is high. We are at a loss as to what to do next. Thanks