I have a Cat with 1.8 Zetec, Twin Webbers,Webcon,Polo Rad etc.
Engine ticks over about 800 per min normally, but yesterday when stuck in traffic for approx 30 mins (moving very slowly) the revs gradually increased to about 1200 for no apparent reason. The Temp did not go over 90 ish. Any ideas, could it be that the under bonnet temp was hotter than normal ?affecting ECU? is anything to worry about?
Mike

Had a similar problem to yours on a Pinto engined Fury.

After much head scratching and checking everything half a dozen times. Turned out to be the throttle cable was run over the top of the exhaust manifold.

Had the effect of heating up the cable outer which expanded slightly increasing it's length, just enough to lift the idle revs.

Only happend when in stationary or still traffic as air flow kept it cool when moving.

Sorted by allowing a little more slack in the throttle cable when at idle.

Cheers

Mike

Mine did that last week - was idling at 1300rpm when warm, also off tune generally.

It turned out to be an air leak between the carb and the head.

As I found out yesterday I'd lost the front lower mounting nut off the front carb. Another nut and washer solved it.

Hope yours is that easy