05 Plate renault scenic cold start problems

[gizmo]

Hi
I have an 05 plate renault scenic privilige 1.6 vvt that has just started having problems with starting when the engine is cold.
The engine fires up then immediately stalls. It will then fire up again and stall immediately again. The next time the engine just turns over and over until I blip the throttle then it will start (but to keep the engine running I have to keep the revs up) with the revs up the engine feels very juddery as though a spark plug is off. When the engine has warmed up (5 bars on the temp display) the engine runs fine although the revs sometimes drop to three bars on the rev counter as opposed to the normal 4 bars. When the engine is running it accelerates as normal.

Has anyone any ideas as to what is going on with my car

Thanks for any help

[Hometune]

The coolant temp sensor may not be operating correctly. It is the equivalent of an old fashioned choke. You would need to put it on a scanner to check the reading it is giving from cold.
Is there any hint of a rattle at all when you first try to start it? As your engine has variable valve timing there may be a problem with the advance unit. Again, a scan would show this up.

[gizmo]

Hometune,

Thanks for the info, I have had it on a diagnostic machine this morning and it throws up an error code for a camshaft sensor (would this cause my symptoms and can i be popped out and given a quick clean and put back in to test) the car does not rattle on start up (like it does with a faulty vvt dephaser)

Any help gratefully appreciated

Gizmo

[Hometune]

No you can't clean it. It works or it doesn't.
This may be the start of a problem with the dephaser or its control solenoid. Often this code can mean the dephaser is failing even if you don't have the rattle.
Maybe try a cam sensor from a scrapyard to test first?
I have one of these currently in a Jaguar garage (don't ask) and it threw up cam sensor. It is the dephaser so will need the timing belt etc doing as well. This one misfires and just does't run right at all.

[gizmo]

Hometune

Again thanks for the advice, it is booked in at my local renault garage to go on their diag equip tomorrow. I had the dephaser replaced (inc cam belt,water pump, pulley tensioner etc) under warrenty when it started rattling so hopefully it isnt that. will post results when I find out.

Thanks
Gizmo

[gizmo]

Bad form to reply to own post but I've had the car to my local renault garage. The result of their diag check is a faulty camshaft sensor. £60+ vat for the diag check but they are halving it to £30 and are charging £45+vat fitted for the camshaft sensor so about £80 ish. Not bad

Thanks for all your advice

Gizmo