Will not idle when hot

[Speedy88]

Hi all, I love renault williams, brilliant noisy engines :D

First apologies for posting a help topic as a first post. I hope to get into the community but at the moment I'm having a really annoying problem!

Firstly the only non-standard things I'm running are a non-standard fuel regulator (ricer ftw) with a gunner fuel map in the ECU.

That aside, everything else runs great. At startup everything runs perfect and it will idle, run fine. Even up to oil temp its fine but as soon as I've run the car around for 15 mins it all starts to go pete tong.

This is particulary apparent if I run it hot and stop the car. Then get back in 5 mins later and start it up again. The idle will go all the way up to 2k, then fall suddenly, almost stall and back up to 2k again. It will repeat this about 3 times and eventually stall.

If I let the engine cool down for a few hours it will be fine later.

I've replaced air intake, lamda, water temp sensors with no change. Also got a refurbished ICV off ebay which seemed to relieve some symptoms but it's not cured the hot running issues.

Starting to run out of ideas now, I've got a standard regulator to go on but other than that... not a clue. Any of you guys know?

[Wobba]

Hmm.

Air leak.
Dodgy speedo earth in the dash.
Bad crank sensor.
Wet ECU.

Air leaks can be heard as a sucking hiss usually, spraying WD40 onto the suspected leak will help as it will change the revs.

There's loads on the site about the earths you need to check under the dash and footwell.

I've had weird rev issues when my crank sensor got metal filings on it, after I had to drill out a leaking core plug just above it once.

Wet/damaged ECU's can cause some weird stuff but it is unlikely that if it is only happening when hot.

[Speedy88]

thanks for the reply, looks like I can rule out wet ECU as I've had this problem for months and disconnecting the speed sensor doesn't make much difference (other than the high revs under hard use).

I'll look into the other 2 though, thanks.

[Speedy88]

Actually probably worth mentioning there is a hiss sound, but it appears to just be the intake (gets worse when I play with that annoying idle mixture screw)

[Wobba]

I had an air leak from the fat ISCV pipe as it connects to the inlet manifold once, but it can be from a few places.

I wouldn't mess with the idle screw, they are set from factory.

I'd give it a proper check over and redo all the earths. Always a good starting point.

Can just clean up the crank sensor and see if it helps.

You checked under the dash already for the little black earth wire?

[Coops]

loose the aftermarket fuel pressure reg as well, totally unnecessary and likely to be adding to any running issues

[Speedy88]

Many thanks for your help, so far I've installed a standard fuel reg, we'll see how that goes. There was a wire going to a sensor under the inlet manifold which was brushing against the crank sensor. Probably a cause, I'll be re-wiring that. Will update :D

[Wobba]

Let us know.

[acerimmer]

like to see whats happens mate, it sounds like mine. But i took out the engine all back together now but something is a miss, but sounds like like a air leak, sounds like from around the inlet????