Question about 2001 Jaguar S-Type
Try to understand if the problem comes from engine or transmission.
If the problem happens only at that speed, then usually it is the transmission
Among other faults that can cause the car engine jerking only at a determined speed there are Throttle position sensor, tranny kickdown solenoid, speed sensor, car ECM (control computer module), etc
Since this kind of fault is difficult to find, a good idea could be connecting the car computer to an OBDII code reader and getting fault codes that can indicate the nature of the problem.
Posted on Jul 22, 2009
Actually this is some what of a common problem not only for your Jaguar but for most vehicles.
The "chugging" you are feeling at that speed, whether the vehicle has a manual or automatic transmission, is the TCC ( transmission converter clutch) if automatic transmission equipped.
The "chugging" is caused by the EGR ( exhaust gas recirculation ) valve function.
As the vehicle accumulates miles or "wears in" , fuel varnish builds up inside the fuel injectors, carbon begins to accumulate on the intake valves and combustion chamber, absorbing the atomized fuel, and creates an uneven burn pattern on the combustion stroke. When the EGR is activated by the engine controller along with the TCC, the uneven combustion is felt inside the vehicle as a "chugging or minor missfire" condition.
I would suggest at 78k you have an ignition system and fuel system tune-up. The spark plugs should be replaced, the EGR valve cleaned and the fuel injectors cleaned with a fuel filter replacement. Your dealer should have the equipment to perform the injection system cleaning which is done with a cleaner and high pressure system, if not try using a high quality fuel system cleaner that cleans the injectors and the combustion chamber of any varnishes and carbon.
The "chugging" your feeling won't damage any components but is more of an annoyance.
If you have the service performed as I described, the condition will be greatly reduced or non-existent.
Hope this helps.
Posted on Jul 22, 2009
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Posted on Jan 02, 2017
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