My 2wd sapphire has developed the usual erratic idle problem, the revs now go up and down when the engines hot or cold.

When hot if I unplug the idle control valve, the engine speed stabilizes. I've gaped the pluges and checked the fuel pressure, reads 51psi at idle. I've also checked the TPS with a volt meter, got a reading of 5v. Can I assume that the idle control valve is at fault? I tried cleaning it, hasn't helped. I don't want to spend £100 on a new ICV just in case it's something else.

All advice is greatly appreciated. I'm new to Cosworths and a bit out of my depth.

P.S. The CO was set recently at MOT station, the plugs however are a bit sooty(Champion QC57C).

 

most likely you CO is at fault
On my 2wd i used to run my CO higher than the MOT limit so it ticked over ok
I take it they lowered the Co reading to pass the MOT

With the idle valve plugged in turn the screw on the ecu clockwise half a turn at a time till the tickover stabilizes...
im assuming you cossie is not standard hence the larger injectors give u a rich CO at idle

Having said all that my escort goes through the mot on a P8 and greys

 

Thanks for the reply Meep Meep. 2wd has stage one chip -31 cone filter and magnex, injectors are standard. Exactly right about the mot tester adjusting the CO. Before the mot the idle was erractic when cold, since the mot the idle is erractic now when hot and cold, and hasn't run properly since the CO was adjusted. Will try turning the CO up as you suggest.

Many thanks

 

I had the same thing Jimbo, started just when cold then did it all the time... I removed the dumo valve & replaced a possible split hose and its only erratic when cold again..

 

When i put my C57's in i had idle problems, but changed the base idle and set the co2 to 3.5 - 4.0 % and managed to iron out the idle prob, Also with regards to the idle valve, take it out and soak it on petrol for the night or WD 40 then put it back in, if it starts to idle erracticly give it a "TAP" with a spanner and it should stop.

Give it a try...


Cheers

Alex.......

 

Thanks Alex. I've noticed with the C57's the idle is a bit lumpy. The idle going up and down however would drive you crazy. I'll have a go at what you suggest, I will take it back to the MOT station to have the CO re-adjusted.

P.S. I like the bit about giving it a tap. I have a big hammer here. LOL

 

you may need to turn the base idle up a bit aswell , I set mine to 850 - 950 rpm.

 

dont forget that the 2wd ecu to lean the co is clockwise and richen it is ant clockwise and the reverse way for 4wd ecu

 

Good info here!!

 

I soaked my ICV in some carb cleaner for the weekend which seems to have (fingers crossed) cured my cold idle problems didn’t even need the beating with the spanner