3000rpm with no throttle. Help!

[DamienW]

Little bit of background. My Clio 182 has been off the road since 2013 when the engine was trashed. I bought it a couple of years ago, put a low mileage replacement engine in it and have been struggling on and off since to get it going. When started it revs to 3000rpm on its own and as it warms starts to cycle between 2000 and 3000 revs. Operating the throttle will increase the revs above 3000 but otherwise it is revving on its own with the throttle butterfly closed. Have checked for codes but nothing showing up. I have tried so many things I am about to give up!! Timing is spot on (set using Renault tools), earths are good, air temp sensor, manifold pressure sensor, ecu/uch, crank position sensor, injectors, dephaser all changed. Any ideas? Wiring? What else to try? Any ideas/ help much appreciated.

 

[JamesBryan]

Sounds like an air leak that.

Either around the throttle body or the upper inlet.

 

[DamienW]

That was my initial thought but I have checked it all over for air tightness about ten times. Got all new gaskets. I'll give it another go though. I am thinking either a major air leak somewhere as you suggest or the throttle body isn't communicating with the ecu causing it to over fuel.

 

[JamesBryan]

Spray some brake cleaner around the joins and see if the idle drops.

 

[DamienW]

Spray some brake cleaner around the joins and see if the idle drops.

Will have a go at that. On checking for leaks I have realised that when the ignition is on, operating the throttle causes the butterfly to be either fully open or fully closed. The throttle body also constantly buzzes. I guess it should operate progressively even when the engine isn't running? Maybe the throttle body is the problem. How to test it?