5 litre vt calais high idle problem

[kasey375]

Hi all im having a problem with my vt calais its a 5 litre with twin 3 inch exhaust slightly bigger cam not sure what it is (was in it when i bought the car). the ignition modual has been replaced to as it was stuffed when i got the car.
When i start the car it idles from anywhere between 1500 - 2000rpm. It does it all the time doesn't matter if it is hot or cold and when im driving it i have to be on thr brake alot because its like cruise control is on and it just keeps speeding up.
When i want to slow down the gearbox goes back a gear and the revs are up again. Sometimes if i free rev it the idle will come down sometimes (not very often) and if i rev it again its back up idling high again.
Also i dont know if this has anything to do with the high idle but my gear changes are real crap like sloppier than normal for a vt auto?
Does anyone have any ideas? im sick of going to mechanics and getting the car back in the same condition.
Any help or advice would be great.

 

[accentstencil]

The first thing I would be looking at is the IAC valve (Idle Air Control), sometimes cleaning it will fix the problem. I know absolutely nothing about the 5 litre V8 but I am assuming it has an IAC valve (also called IAC motor)
The IAC valve is on the throttle body but you will only see the round black part.

 

[kasey375]

Hi yes have tried that took it out and cleaned it and was still the same so got another one and tried that too, still the same.
Thanks for trying anyways.

 

[accentstencil]

Air leaks around the throttle body can also cause high idle, check the condition of any hoses that are connected to the throttle body.

 

[BlackVXGTS]

Make sure that the throttle cable that attaches to your throttle body is very loose - needs to have 10-15mm of play (side to side). If it's too tight it can cause a high idle. You need to lever up the metal clip in the attached diagram which will allow you to adjust the cable.

Sorry, didn't read your post correctly that you had a VT 5l V8. The adjustment is a little different for a V8 - refer to the VT diagram.

 

[lll-HUNTER-lll]

I have seen a few people screw in the base idle screw on the throttle body when they put in their lumpy cams, yours might have been screwed right in

 

[kasey375]

I think if it was the base idle screw in to far then it would idle high all of the time but as it will somtimes drop down to about 850rpm i dont think that is the problem