My brothers RS has had more of its fair share of problems, and we have been trying to sort them all out. Replaced the fan switch (so the fan worked as it should, not on all the time) and also sorted out the dodgy fuel pump wiring that the previous owner bodged!

Went to start it up and it fired fine, but it was idling way too high. I adjusted the screw underneath the inlet manifold so it was idling around 1000rpm.

Went for a drive, and about 2 mins after we went off, my brother said that the idling had dropped right down, to like 500rpm. Pulled over, and I adjusted the screw back so it was up to 1000 rpm.

Went for a 10min drive and all was well.

Then just as we were approaching home, it was clear that at idle it had shot back up to well over 2000rpm.

Limped back home, and again i adjusted it so it went back down to 1000rpm.

But then as it was just sitting there idling on the driveway, the revs dropped down to like 400rpm

Any idea as to whats causing all this bizaare idling?