The last few days I have experienced surging at idle and uneven revs at speed. I have cleaned the throttle body and butterfly but still have the symptoms. I fear the throttle position sensor is failing? Hope I am wrong! Suggestions?
Thanks 187,000 miles on my '99 convertible

 

Could be an air leak (check fuel trims) or a "lazy" O2 sensor.

 

Definitely get us some fuel trims to take a look at. In the mean time get some MAF cleaner and give the MAF a good cleaning.

 

^^ Agreed. It never hurts to start by cleaning the MAF sensor, especially if it has never been cleaned before....

 

On my 2001 XK8 the first signs of a failing TPS were the revs just dropped as no throttle position signal was being sent to the ECM.

Graham