XJR surging/no power
#1
09-03-2022, 02:54 PM
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XJR surging/no power
2004 XJR with 55K miles.
Reversed out of the garage and drove perhaps half a mile. Car running perfectly.
Stopped at a T junction, turned right, tried to accelerate and could not. The car inched forward and when the accelerator pedal was depressed the engine speed increased to perhaps 2000rpm, the car speed increased slightly, and then fell back to barely walking pace. Surged would be an apt description. Pulled on to the hard shoulder. The engine was idling perfectly at 750 rpm in Park. Pressing on the accelerator in Park allowed the engine speed to increase to a maximum of 2500rpm.
Turned around and "tick tocked" home on idle or just above. No check engine light and no Restrictive performance signal.
Back home in the garage checked for DTCs and there were none.
Next day I tried it again with the same surging result except that when I was back on the hard shoulder I turned the engine off, waited ten seconds, started the car and it ran perfectly, back to its old self - except that its not. Its waiting to get me when I'm 100 miles from home.
Throttle pedal potentiometer or throttle body perhaps. Any ideas?
Reversed out of the garage and drove perhaps half a mile. Car running perfectly.
Stopped at a T junction, turned right, tried to accelerate and could not. The car inched forward and when the accelerator pedal was depressed the engine speed increased to perhaps 2000rpm, the car speed increased slightly, and then fell back to barely walking pace. Surged would be an apt description. Pulled on to the hard shoulder. The engine was idling perfectly at 750 rpm in Park. Pressing on the accelerator in Park allowed the engine speed to increase to a maximum of 2500rpm.
Turned around and "tick tocked" home on idle or just above. No check engine light and no Restrictive performance signal.
Back home in the garage checked for DTCs and there were none.
Next day I tried it again with the same surging result except that when I was back on the hard shoulder I turned the engine off, waited ten seconds, started the car and it ran perfectly, back to its old self - except that its not. Its waiting to get me when I'm 100 miles from home.
Throttle pedal potentiometer or throttle body perhaps. Any ideas?
#2
09-05-2022, 06:07 AM
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Don B (09-10-2022)
#3
09-05-2022, 09:17 AM
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09-10-2022, 09:35 PM
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Hi horatio,
Welcome to the Jaguar Forums! It's great to have you with us.
One question is whether your scan tool can read Network codes (U-prefix)? It is possible that a fault such as you describe could trigger CAN codes that cannot be read by a generic OBDII scan tool. It is also possible that you may have transmission-related codes stored that cannot be read by generic scanners.
Your suspicion of the throttle position sensors is good, along with the throttle motor and accelerator pedal position sensors.
It's possible that more than one issue is contributing to your symptoms. Some possible suspects that come to mind, some of which may be harebrained, are:
Electronic Park Brake engaging on its own?
Low transmission fluid?
Clogged transmission fluid filter?
Contaminated fuel?
Clogged fuel filter?
Clogged air filter?
Fuel pump or fuel pump drive circuit issue?
Gear selector cable stretched and not setting the transmission in its detents properly?
Clogged catalytic converter/restricted exhaust?
Other members will hopefully think of other possibilities.
Cheers,
Don
:
Welcome to the Jaguar Forums! It's great to have you with us.
One question is whether your scan tool can read Network codes (U-prefix)? It is possible that a fault such as you describe could trigger CAN codes that cannot be read by a generic OBDII scan tool. It is also possible that you may have transmission-related codes stored that cannot be read by generic scanners.
Your suspicion of the throttle position sensors is good, along with the throttle motor and accelerator pedal position sensors.
It's possible that more than one issue is contributing to your symptoms. Some possible suspects that come to mind, some of which may be harebrained, are:
Electronic Park Brake engaging on its own?
Low transmission fluid?
Clogged transmission fluid filter?
Contaminated fuel?
Clogged fuel filter?
Clogged air filter?
Fuel pump or fuel pump drive circuit issue?
Gear selector cable stretched and not setting the transmission in its detents properly?
Clogged catalytic converter/restricted exhaust?
Other members will hopefully think of other possibilities.
Cheers,
Don
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