I have a 98 XK8, after sitting for 2 weeks or so, I started it and it started ok. But when I step on the gas, nothing happened even though it is idling ok. turned it off and restarted it, and everything was OK. drove it for a mile or so, then a stop light the same thing happened. No power when stepping on the gas, but engine was still idling fine. restarted it and all ok. It happened a few times again in the me he last couple of days. Any ideas where to start looking? Gas filter, accelarator,??

 

More specific details would help, no power do you mean the car won't move? or does the engine not rev? or ??

 

I meant that when I step on the gas peddle, nothing happens, the engine is still running. The engine is idling fine but no additional gas is getting to it when I step on the gas. I turn it off and restart it, and it works fine.

I had the full gas throttle body rebuilt last week and things has been fine until now.

 

As you know, this car is throttle-by-wire. Pressing the "gas" pedal just informs the ECU that you want to accelerate. There is no direct cable to the throttle body. I would assume a slew of codes would be generated in such an instance. I would advise you to get a diagnostic reading of all the codes, especially when this problem occurs. Not all codes get stored for later retrieval. Have you had the throttle body rebuilt by a reputable place?

There are probably a number of things to check for zero dollars before spending money on diagnostic. The throttle sensor is near the brake booster. The cable from the pedal can be adjusted. From memory, some calibration can be done with ignition on, engine off, by slowly pressing the pedal all the way to the floor several times. This informs the ECU of the whole range of the sensor, reputedly.

Also, there is always the "hard reset" procedure that can cure some problems related to the computer system remembering things that are no longer accurate.

Folks have sometimes had luck with re-seating or use of contact cleaner on the throttle body connectors as well.

Best of luck, keep us posted.

 

Sounds like a place to start, check connections etc, btw that would have been a good piece of information to provide up front

 

Actually the throttle body was rebuilt last year not last week, and it's been running fine since.

How is a hard -reset done?

 

Disconnect the battery positive lead and hold it to a ground for 30 seconds or so, but I don't think that will help. It has to be a sensor problem, because you're pressing the throttle and the ecu has no idea.

 

Sounds like the tps maybe loose, as far as fuel put a pressure gage on and see if your above 55 psi to ensure pump / filter is flowing properly.

 

Random thought, but it also sounds similar to the behaviour that Tsb 303-s514 was intended to address. Depending on VIN, it was either a replacement TB or software reflash. Perhaps yours falls into the latter category and it was never performed?

Jim's post here contains the TSB which will help you identify: https://www.jaguarforums.com/forum/x...34/#post141960

Mike