Weird starting fault when engine warm?

[general_piffle]

Hi, I wondered if anyone had experienced the same thing or knew what this might be?

Say I drive to the shops, do some shopping, then go back to the car and start it up when the engine is still warm it starts but the revs rise and fall rhythmically without me touching the pedals. The only way to stop it is to turn the engine off and on again or sometimes if I give it some revs it settles back to normal.

It feels like a sensor of some description is playing up and feeding the engine false information. It's been going on for about 2 years but has been getting worse recently and will need fixing soon.

Any ideas as to what it might be?! Cheers.

[itavaltalainen]

what engine code? mileage? what condition is it in (serviced at all)?

[general_piffle]

16v GTI MK3 from 1994, 69,000 miles, serviced 3,000 miles ago (still had the fault then but not as frequent as now) oil and filter change about 10 miles ago.

[VR6_Wherry]

Have you cleaned the throttle body out with carb cleaner?

[general_piffle]

Have you cleaned the throttle body out with carb cleaner?

No I haven't and to my knowledge although the car is very low miles for its age this has probably never been done. Could it simply be this? Cheers.

[thai-wronghorse]

Potentially, yes. Also worth giving all the breather hoses and idle stabilisation valve a good clean.

[general_piffle]

Potentially, yes. Also worth giving all the breather hoses and idle stabilisation valve a good clean.

That sounds promising. Where does the idle stabilisation valve live? Cheers.

[thai-wronghorse]

It's the cylindrical unit infront of the intake manifold (with the black plastic ignition lead holder removed)

[thai-wronghorse]

Beneath this

[general_piffle]

that's really helpful thai, thanks. I'll get them to have a look at this next service, hopefully it'll be an easy win