Slow return to idle - mk1

Technical Area Engine, Transmission, Exhaust etc
2

Hello,

My mk1 1.6 has been running perfectly until yesterday. Now it’s doing a really annoying thing where after running at higher revs (just normal driving, anything over 1500rpm) the idle speed falls to 1500rpm, then after a few seconds drops slowly back to a rock steady 900/850rpm where it always used to idle. The engine is fine apart from this, pulls like a train, etc.

Now yesterday I had some welding done on the car (battery disconnected) so I’m terrified the ECU is fried, but I’m sure it’s much more likely to be some kind of sticky IACV (or whatever it is that controls idle). At least I hope it is.

I’ve got a Greddy turbo on the engine, if that makes any difference at all.

So any ideas - what do I need to drown in carb cleaner/WD40/oil to fix this? It was too dark last night to have a look, but I have a whole extra hour of day light this evening for car fixing…

3

 Don’t use WD 40.

4

 It’s OK, I don’t have any WD40.

 

I don’t have any idea what may be wrong though (no time to even look at the car last night).

5

 

 

Have a read of this.

http://www.mx5oc.co.uk/forum/forums/t/233.aspx

If this doesn’t fix it get back to me.

6

I managed to not find any time at all to fix this, so had to take it to Donington for round 1 of the Bristish Drift Championship with comedy idle driving me mad the whole way there.

Then it fixed itself out on track and has been perfect ever since - idle falls straight down to 850rpm and stays there steady as a rock. Amazing.

7

The good old Italian tune up works again[;)]