XKR - Intermittent issue: No response from throttle pedal.
Discussion
Hello all. I acquired a late 98 XKR at the end of last year. It's an absolute beauty and I'm enjoying ownership so far, which has included various gremlins to trace and fix. Thank goodness for the knowledge on internet forums!
In the 500 miles or so I've driven the car, I've twice had an issue which is causing me to scratch my head. After a short period on overrun - both times on a dual carriageway; once when on a downhill stretch and another heading towards a roundabout, the car fails to respond to any input from the throttle pedal. The engine speed will eventually drop to idle and the car will come to a halt. The car does not go into any failsafe mode (no warning lights) and no diagnostic codes are being recorded. If I restart the engine, it'll behave itself and I can continue my journey.
From some internet sleuthing, I've come across the Jaguar TSB 514 (http://jagrepair.com/images/TSB/Jaguar%20Service%20Action%20S514.pdf), which appears to be a very similar issue, with the exception that the car does not stall as described in the TSB. When stopped, the car will just sit comfortably at idle speed, but will not respond to the throttle pedal unless I restart the engine.
Has anyone come across this before?
In the 500 miles or so I've driven the car, I've twice had an issue which is causing me to scratch my head. After a short period on overrun - both times on a dual carriageway; once when on a downhill stretch and another heading towards a roundabout, the car fails to respond to any input from the throttle pedal. The engine speed will eventually drop to idle and the car will come to a halt. The car does not go into any failsafe mode (no warning lights) and no diagnostic codes are being recorded. If I restart the engine, it'll behave itself and I can continue my journey.
From some internet sleuthing, I've come across the Jaguar TSB 514 (http://jagrepair.com/images/TSB/Jaguar%20Service%20Action%20S514.pdf), which appears to be a very similar issue, with the exception that the car does not stall as described in the TSB. When stopped, the car will just sit comfortably at idle speed, but will not respond to the throttle pedal unless I restart the engine.
Has anyone come across this before?
There was a saftey recall from Jaguar regarding throttle bodies on pre-2000 AJ 26 engines that occasionally stuck shut on high vacuum overrun conditions because the actuating motor wasn't powerful enough to overcome the vacuum the engine was pulling when the throttle was subsequently opened. They should have all been replaced with the later AJ27 design.
As suggested cleaning as much of the inside of the body and the butterfly valve you can access - you can open the butterfly with finger pressure, operating the throttle won't move it - with a wad of tissue and carb cleaner might be all you need to do.
There's a 2.5mm calibrated crank air bleed hole inside the stub on the n/s bank cam cover where the part load breather pipe attaches.Pop the pipe off and gently clean any crud out the hole with a 2.5mm drill bit.
If that's blocked you may have a slightly raised manifold vacuum and that could be contributing to the problem.
As suggested cleaning as much of the inside of the body and the butterfly valve you can access - you can open the butterfly with finger pressure, operating the throttle won't move it - with a wad of tissue and carb cleaner might be all you need to do.
There's a 2.5mm calibrated crank air bleed hole inside the stub on the n/s bank cam cover where the part load breather pipe attaches.Pop the pipe off and gently clean any crud out the hole with a 2.5mm drill bit.
If that's blocked you may have a slightly raised manifold vacuum and that could be contributing to the problem.
Thanks, both. That makes a great deal of sense. I presume Steve the safety recall you mention was the same as in my original post? If so, the explanation is really useful, as I was scratching my head as to the similarities in the circumstances both times when the fault occurred: come to think of it, they both were after a short period of fast acceleration (not WOT), followed by deacceleration on overrun, so that chimes with the vacuum scenario - I think!
Gassing Station | Jaguar | Top of Page | What's New | My Stuff