Hi, My car ('83 1.8 GTi) starts OKish in the cold and will idle nicely round 1000rpm for the first few minutes, but by the time i get to the first junction down my road the idle has dropped considerably (sometimes it cuts out totally). Any suggestions as to what this could be? hope this makes sense Doc
sounds like you've got your idle screw wound in too far. when the engine is cold it should idle higher than when warm because the cold start valve is letting more air through. once the car it warm you need o set the idle.
Thanks GTi. That sounds quite easy to fix, however, the idle is fine once the engine has warmed up. could it still be the screw?
It'll be the warm up valve on the back of the inlet manifold. The cold start valve is the fifth injector on the end of the inlet manifold which gives a squirt of extra fuel to start it. My mk1 was exactly the same and a new warm up valve sorted it. They're quite expensive though!
thanks danger, how does the warm up valve work then? does it control the cold start valve in some way? did the new warm up valve help starting at all? cheers
No it didn't help starting, it just made it idle properly when cold. Like GTi said, when the engine is cold the valve lets more air in, then gradually closes as it warms up. I'm not sure how (or if it is connected to the cold start valve) but I think the cold start valve is connected to the thermo time switch, which is where it tells it how/when to operate. Anybody else care to correct me or add to this please?
you are right, the cold start valve is connected to a thermo time swith. this only helps out when you leave the car to idle when cold. not sure about the fifth injector so i'll not comment on that.
