Sorry to be a pain but.....

The new car is great, drives lovely except that at idle, even when warm the RPM rythmically goes from 1000, down to 500, up, down, up, down etc. etc. etc.This is rather disconcerting.

Any ideas greatly appreciated!! It is 93, 414 Sli with mpi.

Check the coolant temperature sensor is connected (On the underside of the inlet manifold)

Otherwise check for air leaks, broken vacuum pipes etc

Otherwise a Health Check on T4 maybe called for >=(

I have exactly the same problem on my 97 214Si 16v. I'm taking it to the local dealer on Saturday for a healthcheck - I'll let you know how it goes.

I had a similar thing on my 416 before the head gasket went, but thats another story.
I wish I got it check out rather than ignoring it.

Yeah....thinking about it, it could be caused by air pockets in the cooling system confusing the temperature sensor...due to a blown head gasket >=( >=(

My head gasket has just been changed so I can rule that out (thank god):).

Dave, how much should a diagnostic check cost at a main dealer? I've been told they'll do an hours testing on the engine. Is this the T4?

Just had a T4 done on my 200. It was the inlet sensor - bad earth! It's now running beautifully. Well worth it!

Probably no more than 30-45 mins of work for a healthcheck/tune up

where is the earthing point?

Matt

There was a concern with the battery to body earth connection back along - this would give rise to poor starting etc This affected 200 and 400's

It's the little connection from the battery negative terminal to the bonnet slam panel

Remove it and give it a scratch up with some emery cloth and refit it. Try this first.

The fault reappeared on thursday. I started the car 1st thing in the morning and the idle speed was all over the place, it stabilised slightly after about 15 miles but was still high at about 1500rpm. I pulled over, turned the ignition off and waited about 30 secs. Restarted the car and it was perfect and has been ever since!!!

It seems like some kind of stepper motor fault, is this likely, can they stick, would it give these symptoms?