Rough running again!

[Tryw]

Hi Guys, an ongoing problem i have with my s3 is intermitant rough running like petrol starvation. Loss of power,jerkiness, was only doing it after 30 mins or so but just seems to have got worse. It starts pretty much when ticking over now, revs drop and a low hissing like air escaping happens. After blipping the throttle the sound goes,but problem soon returns :-( very frustrating!! I have replaced the throttle pot and dont really know what to do next?

Cheers Rob

[Scoobimax]

Have you checked the connector to the TP?

Might seem daft but that's what mine was down to

[Top Gear TVR]

Isnt a TP what indians live in?

[steve j]

Sounds very much like an air leak, especially as you can hear a hissing sound.

[Tryw]

what i cant understand if it is a air leak why does it only happen some times and not others?

[mep12345]

Tryw said:

what i cant understand if it is a air leak why does it only happen some times and not others?

Perishing rubber could leak only when flexing in certain ways or when warm. You can also get the hissing sound through the ISCV if it is trying to control at almost fully shut and also through the AFM as they shut off if the car "almost" stalls then have to open rapidly as the revs rise when either the throttle is touched or the ISCV takes control.

I'd clean the ISCV if you haven't already and do it properly by splitting it at the centre section (where the two screws are) and washing out both sides with carb cleaner then using a cotton wool bud carefully clean the "valve" assembly. Easy job done in 20 minutes.

Then clean the AFM flaps. Again use carb cleaner and carefully use a tooth brush and cotton wool buds on the stubborn bits and the air temperature sensor respectively. This takes a little longer as you either have to take them off the car, remove the bonnet or be a contortionist to get to them properly.

HTH

Mark

[Spathodus77]

Dodgey electrical contact to the AFMs or AFMs not adjusted correctly? Can you measure CO and see if the engine is running lean/rich?

Ralph

[Tryw]

Thanks for the advice guys! I will have a poke around and do a bit of cleaning and post a result, cheers!

[Barkychoc]

Brake servo would be my first port of call.

Look underneath where the road crud hits it.

If its playing up at idle ease the hose out of the rubber grommet and put your thumb over the end to see it the idle settles down.

[Oldred_V8S]

Servo hose?