Its a 1990 Metro GTi 16valve 1.4 K series engine single point injection. Its got 92000 miles on the clock and is serviced by a Rover dealer every 12000 miles and I change the oil every 6000 or months depending on which is sooner.

The Problem:

When starting from cold the car idles perfectly and when driving off revs are very smooth, but place the car under load and the car judders as if mis-firing. But when warm it's perfect. I have a K&N filter element which is clean and Splitfire plugs which have 8000 miles on them, I mentioned this to the Rover dealer at the last service which was in the summer and a fault was found with the air flow sensor which was replaced. I have since been back to the Dealer to have another check for the problem but they cannot locate it. I am worried that the mis-firing is detonation and as there are steep hills outside of my work place so have to place the car under load.

Could it be the ignition leads ? Or rotor arm

Please help !

Thanks for your question, Your service schedule is excellent, and shouldn't be the cause of your problem, that's certain, it could quite easily could be something to do with Spark/Ignition, How long has it been since the leads were changed ? if they haven't been changed since new or in the last 50000 miles it almost certainly is a lead problem, the Leads become brittle and crack internally causing several sparks throughout the leads length, and in doing so makes the spark at the Plug very weak. Equally it could be Distributor Cap or Rotor Arm problems, again if they haven't been changed in the last 50000 miles they almost certainly need changing, the centre Carbon in the cap could be badly worn, or the electrodes in the cap could be worn, this causes the Ignition to struggle under load, there could also be tiny cracks in the cap, though this usually causes bad starting particularly in damp weather.

I think you are looking in the right direction, while doing the Leads and Cap etc have a look at the Air Filter, this could also be causing some problems if it's blocked, though this should have been being changed by the dealer at each major service, if it's been done properly.

I trust this helps, please let me know, I'm sorry I'm a bit late answering, but things have been a bit hectic recently, good luck.

Regards Bill