Djed710

I hope I'm posting this in the right section, it's the first time iv ever posted anything in a forum! Iv got a 2wd saph cosworth that iv recently rebuilt engine on. Done about 600miles since the build, all going well until now. Engine won't drop below 1200rmp at tickover. Iv wound the idle air screw under the throttle butterfly all the way in and the throttle stop is wound all the way down so I no the throttles closing fully. The idle control valve isn't stuck because if I remove it but leave it plugged in you can see it move fully open then closed if you turn ignition on and off. If you unplug the valve whilst engines running it makes no difference to the idle, it stays at 1200. I suspected it to be a vacuum leak so checked all pipes ect and tried spraying carb cleaner round the manifold gaskets. If I spray it round the injector seals it raises the revs slightly which must mean it's drawing some in but I pit new o rings on them and it stil does slightly when you spray round them. Do u think this could be enough to cause the high tickover? I was wondering if the coolant temp sensor was faulty could that cause it to run on cold start all the time or would cold start use the idle control valve to raise revs therefore they shud drop to normal if I unplugged it?

Sorry about the long post, just trying to giv as much info as I can! Thanx for your time! Hopefully someone might be able to shed some light! Thanx. Ed

oldford

Coolant temp can cause this. Measure resistance warm or voltage with running engine.
Voltage must be below 0,5 volt when engine is warm.
For resistance see: http://www.bigturbo.co.uk/main4.htm
You can also measure voltage or resistance at the ecu connector. Use pin 29.
See: http://www.bigturbo.co.uk/main6.htm

Djed710

Thanx alot il giv that a try later on n see what the result is. Cheers oldford

studabear

also is the tps set correctly?

Djed710

What position should the tps be set in? Thanx

martysmartie

iTrader: (1)

Won't be the CTS, only way idle can raise is through throttle or via ISCV, unless you have an air leak elsewhere. The fact you have disconnected ISCV and the revs remain unchanged show it to be an air leak proved by the revs raising when you spray WD40.

Check the inlet manifold gasket and the plenum gasket.

Martin

Chip

iTrader: (3)

Agreed sounds like an airleak to me, it HAS to be getting enough air for 1200rpm from somewhere.

Djed710

Thanx for all the advice. Turned out it was an air leak after all, not from the injectors tho, the carb cleaner was running down number 1 injector and getting drawn in through a tear in the bottom of the plenum gasket, right out of sight ! Gonna set c o at work tomorro and hopefully should run sweet... For a few miles before Il be needing to put another post with my next problem!!

Could anyone tell me what position I should hav the tps set in? Iv currently got it so it's as much in the 'off' position without it starting to hold the throttle open. Also is the base idle ok around 800?

Thanx again for the help with my first post.

martysmartie

iTrader: (1)

What do I win? haha

Glad it's sorted.

The TPS doesn't do anything to the throttle, rather it moves with the throttle the signal given (0-5V) is used to determine the angle of the throttle. I would set the base idle a little higher say 950RPM, also make sure the cooling fans are not on when you check the CO. The TPS reading should be around 0.6V at WOT.

Martin

Djed710

Thanx Martin, had emissions tester on it at dinner time n found out it was running really lean too. It was around 0.2 instead of 1-2% which I believe it should be so adjusted it to around 1.8 and it's running nice now! Do u think this could be why it was holding back a bit under acceleration? Sometimes it would go really well and other times it'd be a bit flat towards higher rpm.

Thanx. Ed

martysmartie

iTrader: (1)

Yes it would it also was dangerous like that as you could of ended up with a meltdown, that probably would explain the lack of top end power as you don't have enough fuel. The CO is specific to the chip you have, most chip authors do still retain the standard CO though I am pretty sure MSD is one example.

I actually said wrong info for 2WD in my previous post at WOT the TPS reading should be 5V, I had a mad moment and said 0.6V as this what the 4x4 is as they are the complete opposite.

Martin