Fast idle when warm

[Jammiedodger]

Was hoping someone may be able to help...

Over the last few weeks, once the car (1993 1.6 mk1 Eunos) has got warm, the idle speed only drops as far as 1600rpm.

When the car is cold, it idles nicely at just under 1,000rpm, but as soon as warm and pulling up at junctions etc it rests at 1,600 or higher.

There are no other symptoms (e.g. rough running etc), but I'm pretty sure it may be using more fuel than usual (although this could be in my head)...would I be right in thinking this might have something to do with the Air Flow Meter?

Is there any way of testing it?

Cheers in advance,

Jamie

Edited by Jammiedodger on Monday 2nd May 12:19

[MX-5 Lazza]

My money would be on the green engine temp sensor on the back of the block. Nice & cheap and easy enough to DIY though awkward to get to.

[Jammiedodger]

MX-5 Lazza said:

My money would be on the green engine temp sensor on the back of the block. Nice & cheap and easy enough to DIY though awkward to get to.

Ah ok thanks Lazza, I'll do some research into that...never heard of it being an issue before.

Any other ideas at all?

[MX-5 Lazza]

That temp sensor would be the number one suspect. When they fail the ecu is being told that the engine is always cold so it runs rich (high fuel usage) and will keep the idle control valve open (idle high).