High idle on startup.

[wheels]

When the truck is cold, and i start it, idle is at ~1500rpm, and after a minute it slowly drops to reach normal ~700rpm. What could be causing this. It didnt change after a plugs/wires/cap/rotor tune up. Thanks

 

[Mtn Z]

Re: High idle on startup.

Pretty sure it's supposed to idle a little high when it first starts up. Mine does anyway and then idles down to 700 or so rpms after about the same time period you said.

 

[bezerk]

Re: High idle on startup.

correct

 

[DOMN8R]

Re: High idle on startup.

Like everyone said it's normal to idle high at first - I think it was designed that way to help the engine warm up.

However, I have noticed that a small vacuum leak can cause high idle, especially on startup. If you don't have any other symptoms of a vacuum leak (cruise control, hvac issues) then I wouldn't worry about it.

If you haven't already I would recommend investing in datamaster, then you'll know really know how your truck is running and if there are any issues.

 

[mrweelr]

Re: High idle on startup.

Mine idled around 2500 when I first put my motor back together. Turns out the IAC valve got screwed when I cleaned out the throttle body while it was apart. I ordered a new one from http://gmpartsdirect and it solved the problem immediately.

 

[jbone]

Re: High idle on startup.

Same here idles high when cold and slowly drops, I forget the reason but it is supposed to do that. The onlything I havent figured out is why mine bogs down and almost stalls then climbs again when its cold, then when it warms up its fine :dunno: