Engine idle advice 1.8 NA

[vrsmxtb]

Just had an engine swop on my mk1 1.8 and want some advice on an idle issue. On start-up the idle is very lumpy and after a few seconds it rises to about 1000rpm almost like a rich choke. The engine also hesitates quite badly when first driving for about 30secs to a minute, again like a too rich choke. It seems to settle down once its been running for a while, although the idle still seems to waver until the engine is really up to full temp.

The other thing it does is when you come to a stop the revs hang at about 1500rpm for a couple of seconds before falling to a normal idle.

It's had new leads and seems to run fine otherwise. Any ideas?

[NiceCupOfTea]

There is a procedure to reset the idls speed involving the diagnostic connector under the bonnet - check the Rod Grainger bible. Good place to start.

Have you checked for vacuum leaks? Check all pipes seated properly and the intake system.

[MX-5 Lazza]

As above. Make sure there are no vacuum leaks between the throttle and the MAF first but it sounds like it needs the idle resetting properly.

[Eighteeteewhy]

I had a similar problem when I first had mine. A bit different though, it would stall when you came to a stop. Used the suggested website to reset the idle and it's been fine ever since.