Bad vibrations

Q My 2007 Jaguar S-type has an annoying vibration through the accelerator pedal between 1250 and 1500rpm. The automatic gearbox has been rebuilt and there are no clunks when drive is taken up. Any ideas? Stewart Shackleton, Durham A The accelerator pedal is mounted on the bulkhead and has no physical connection to the engine – it’s just an electrical potentiometer feeding a signal to the ECU. What you’re encountering, therefore, is probably a resonance from the bulkhead or floorpan.

Being related to the engine speed and not the road speed, we can eliminate the wheels, propshaft and gearbox (though perhaps not the torque converter) from our enquiries. It’s most likely that some peripheral engine component is making contact with the bodyshell.

There could also be a slight engine imbalance at the rpm range in question due to a minor fault in the of the fuelling or ignition system.