Having problems with your 2004 Jaguar S Type ?
When im stopped edcar jerks foward as if i was hit from behind
The\012following are the general instructions on the start of diagnosing any\012electronically controlled engine or transmission problem.
The\012engine and the automatic transmission (transmission control is only\012for automatics, engine is still computer controlled no matter the\012transmission type) in this vehicle are computer controlled and in\012most cases when a fault occurs a fault code is stored in the memory\012of the computer control module. There are exception to this, such as\012the Mass Airflow Meter and fuel pressure problems. What must be done\012is to have all the basic testing done such as a scan of the system\012for fault codes as well as a check with a live data scanner tool for\012engine functions that are not within range of normal, a trained\012technician is required to know what is correct and what isn't, then\012based on careful diagnostics done from a factory repair manual the\012correct part is replaced or the wiring repaired or the computer\012replaced (known as the PCM or ECM,ECU), which is very rarely the\012problem. Other basic checks must be done as well such as mechanical\012problems with the engine as well as engine state of tune and mileage\012on the engine. The transmission can have mechanical issues as well\012such as no gear engagement at all or a failed pump or other pressure\012related problems. Also engine mechanical problems can and do cause\012many drive-ability related problem such as rough idle and other\012symptoms.
If no dash lights come on, like the ABS or ATC, it may be mechanical and require an undercar visual inspection of the underside. Including the rubber donut connection on the back of the transmission. There should be no cracks in that, and the driveshaft being of a collapsible nature, should be checked for damage, and the rear suspension should be checked to make sure nothing has broken, torn loose, or lost a bolt.
If the condition occurs when shifting from forward to reverse or reverse to forward, a broken engine mount will allow the engine and transmission to wind up a little bit, and then settle down- which can give a feeling as described.
If the ABS lights light up when this occurs, it could also be a stray signal to the ABS module from a loose wheel sensor, corrosion on a connection, collected filings on a sensor, or even a damaged sensor or sensor ring.
It is also possible the throttle position sensor or the pedal postion sensor are a bit dirty or worn, and it is even possible the variable valve timing system may not be transitioning smoothly to normal orientation.
If there are error codes to be read, they would give better clues, and the more sophisticated scanners as are used in dealerships are what is needed.
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