5ltr V8 In VS Caprice Won't Idle - ??????

[The Harvester]

Hey there, I just got hold of a '98 SII VS Caprice with a 5ltr V8. The engine was running great and still does but it will not idle anymore. It starts straight away and still runs perfect but if I back off the throttle while it's in Park and also when I'm driving as soon as I back off it stalls. This probably sounds silly but is there such a thing as an idle sensor or something like that. Any suggestions what's going on with this engine????? Cheers

[levymetal]

late reply - but there's an IAC (idle air control) valve on the bottom of the throttle body. just take the throttle body off, and look underneath. there are only 2 things hooked up - IAC and TPS (throttle position sensor), and you'll know which one the IAC is. take it off and clean the pin with carby cleaner. also clean the valley that the pin sits in. see how that goes to start off with.

[ScoHar]

check all your vacuum lines, the ones that run down the middle of the manifold.

[Helicopter]

A brand new IAC motor will cost you around $100 from Holden. Alternativelly try a wrecker. I replaced mine about 1 month ago. After removing and cleaning the old one using degreaser, I found that I was unable to push or pull the little plunger in/out without using excessive force.

The plunger on new one moved relatively easily, so I suspect in the old unit, over the years the gunk worked its way into the stepper motor assembly making it operate sluggishly which resulted in intermittent stalling as the plunger could't move fast enough to adjust the idle speed.

Just a suggestion.

Cheers