Focus ST170 Intake manifold blew off...

[Flat_Steve]

Had a strange occurrence starting the car yesterday. As soon as I turned the key there was a misfire and the car struggled for revs and sounded terrible - I turned it off and had a look, and the intake manifold going into the block was clean off! The RAC man managed to put it back on and it's running again, but the engine management light is on and it is fairly lumpy below 1500 revs. Above that it seems fine but I'm scared to drive it in case I do damage.

Does anyone know of what could cause the intake manifold to blow off like that, and what could be causing the lumpy idle before I take it to the garage next week? I've done some research on various Focus/ST websites but can't find a single mention of this kind of problem.

Edited by Flat_Steve on Thursday 20th August 16:59

[Zad]

If the engine had been worked on, I would have said the cam belt / chain had been replaced 1 notch out on the inlet camshaft. Maybe the tension roller has collapsed and it has jumped?

[Gareth350]

I agree, sounds like the belt may have jumped a tooth, will still run, very lumpily, causing the timing to go out. Wouldn't drive it until you get it checked out. If it is that, a new belt & tensioner is a must.

[Flat_Steve]

Cheers Zad and Gareth - that's a very good suggestion, it'd certainly account for everything that has happened. If that's what has happened then I guess I can count my lucky stars that the cambelt didn't snap!

Edited by Flat_Steve on Friday 21st August 00:27