This is going to sound ridiculous, but my revving/idle issue appears to have been solved by...
...fitting a new instrument dial cluster (MPH/Revs)
The car was bought and registered in the UK and is left hand drive. Even so, the car had a KM speedo. Going over the history and old MOTs for the car this has always been the case. I bought the car with the idea that I would change to a MPH speedo as soon as possible.
On monday I changed the clusters over, turned the car on and instantly I could tell the difference. I have noticed the following:
The rev counter responds much quicker when you start the engine. With the KM clock, it felt like there was some lag for the rev counter reporting. Not it jumps almost immediately to 800RPM
The car feels much smoother at idle and the rev counter stays firmly at 800RPM. Before it would idle between 1000 and less that 500RPM and generally feel rough.
The most important difference is the engine now responds to the accelerator. I can floor the throttle and without hesitancy it revs all the way to the red line (this is at idle). Gone is the surging and dying of the engine and the inaccurate dial reading as experienced pre-new dial cluster. It's like a car transformed.
I'd be interested to hear if anyone has any experience of this or has a hypothesis as to why this might happen? All I can think of is that the KM cluster unit had something wrong with the electrics which affected the whole car. Other than that I can't see how this would have solved the above engine issues.
Yours. Confused. Adam