VT odd idle

[Brett McRae]

My brother has a 1998 VT excutive auto 3.8 ecotec 120 000km on engine 220 000km on the rest when it stands and idle's it will idle smoothly then it will kick it's revs up to about 1500rpm then it would drop back down to 800rpm, does this both when the airconditioner is on or off. Any suggestions would be helpful.

[Poms308]

My VT was doin that not too long ago it was a spark plug lead wasnt plugged in all the way made mine have a lumpy idle goin up and down, has your brother changed the throttle body?

[Brett McRae]

thanks for the reply havn't had time to check the forum, Umm not sure about the throttle body i will have to contact him and ask to check the service records but i don't know if they would have kept the throttle body from the old engine or put the throttle body from the newer engine. The spark plug lead i check them today and they all seem to be in place and just wiggled them and tried to push them further i will run the car tomorrow and see what it does, it only does it when it idles for about ahh 3 or so minutes it will kick the rev up smoothly then smoothly lower it then it will be fine for another 3 or 4 minutes then do the same. It has only done it since the fuel injectors were cleaned cos it has a bit of a rough idle so it got a good service and the machnic advised my brother to get the injectors cleaned and so we did, it idles smooth now just kicks it's revs.

[dman]

what VT does idle smooth?

[Brett McRae]

all of them, they are a commodore :P the engine itself idles smooth it just as i mentioned above kicks it's revs up for no reason

[sedgewik]

it could be suken air between the air box and throttle body? make sure all hoses are clamped tight