Engine revs to 4krpm when starting when warm

[LegoHead]

It's always done this. If I dont let the car cool down for an hour or more when i restart the car when it's warm it revs itself upto 4200rpm and doesnt drop.

If I use the biting point on the clutch in 5th gear I can drop it back down again.

I am ruling out air leak as it has never ever done it while cold..

Any ideas?

 

[ijaen]

Very dirty idle speed control valve? sticky throttle body?

 

[LegoHead]

Very dirty idle speed control valve? sticky throttle body?

I changed the throttle body for a clean one. This car doesnt have an idle control valve.

I dont understand why it only does it when warm.

Maybe something to do with sensors?

 

[ijaen]

I changed the throttle body for a clean one. This car doesnt have an idle control valve.

I dont understand why it only does it when warm.

Maybe something to do with sensors?

right, does it have the electronic throttle thingie?

I'd take it to renault so they connect it to the clip computer and have a look when its warm...have the car to do it when they are looking at it...

 

[LegoHead]

right, does it have the electronic throttle thingie?

I'd take it to renault so they connect it to the clip computer and have a look when its warm...have the car to do it when they are looking at it...

I want to do that as a last resort.

 

[Russ_16v]

weird mate, problem is with a car so highly modified as yours it really could be anything,its gotta be sensor related im guessing though get it running and spray wd40/carb cleaner around and see if you can find some air leaks just to rule that out

 

[tim124]

Air leaks that change with temperature are very common. As the different metals expand gaps can open up.

 

[ChrisD172]

Had exact same problem mate

Was the throttle pedal unit in the footwell, think the potentiometer goes in them, bloody fly by wire throttles

 

[LegoHead]

I'll check all the above, but also wondering if it could be the fuel pressure regulator? I have trouble starting the car unless i do it when it primes it wont start.

I had a look at the injectors and they dont look like they are leaking when I prime the fuel pump.

I will get to the bottom of this eventually!

 

[Russ_16v]

cant see it being the reg mate, my mates reg was over 5 bar on his twin turbo sierra, but it didnt change the idle (its back to 3 bar now lol)

i cant see it being the injectors either, more fuel going in on its own wont make it rev that high, i still say a sensor fault, does it struggle at that revs or does it simply rev up like you were holding the throttle?

 

[LegoHead]

cant see it being the reg mate, my mates reg was over 5 bar on his twin turbo sierra, but it didnt change the idle (its back to 3 bar now lol)

i cant see it being the injectors either, more fuel going in on its own wont make it rev that high, i still say a sensor fault, does it struggle at that revs or does it simply rev up like you were holding the throttle?

When you start it the revs climb then keep climbing and stop at around 4200rpm, if i touch the throttle the revs go even higher.

It's not struggling at that level.

 

[LegoHead]

Any more ideas?

 

[ditz]

does your gearbox have a speed sensor? if so unplug it and see if it still does it.. fords suffer with a similar issue and its sometimes heat related also

 

[ditz]

its worth seeing too,,,, when its actually doing this.. pull the boost pipe off the t/b and see if the butterfly is actually being opened making it rev high.

that will tell you if its the ecu making it rev...

if its shut.. it could be something a bit more interersting like a leaky injecter maybe dribbling fuel in to the inlet slowly thus making it rev up when you first start it???

airleak when something expands?

you get the idea