strange sputtering plus high idle

[69camarokid]

I have a rebuilt 65 trans am LT1 t56 with a cc305 cam and bolt ons in my 69 camaro.

Ever since i got the new engine running it has had an issue with idle when i first start it. It will idle near 900 as son as its started then after i start to drive it the idle flucuates between 450 and 650RPMs and almost dies. after a minuite or so the idle will jump back up to 900 and stay there with no problems.

This idle flucuation lasts longer in colder weather and if the car has been driven earlier that dayand the engine is still warmed up then it will idle at 900 with no flucuation.

any ideas????
oh, nadive also had the computer flashed for all the additions to the engine.

thanks

[69camarokid]

i had originally thought it may have been some kind of vacuum leak that caused the engine to run its self higher but after a smake test the vacuum lines were shown to have no problems.

no one has any ideas?

[69camarokid]

no ideas at all?

[Scott Parkhurst]

I'd check the idle air control. If it's dirty and can't seal, the computer will make the engine 'seek' - which is what it sounds like. Once it warms up, it's no longer used.

I'd locate and remove the IAC valve and clean its sealing surfaces.

[Rybar]

I'd check the idle air control. If it's dirty and can't seal, the computer will make the engine 'seek' - which is what it sounds like. Once it warms up, it's no longer used.

I'd locate and remove the IAC valve and clean its sealing surfaces.

Yup, what he said. I had the same problem with my old LT1 4th gen.

[69camarokid]

thats a good idea, but something i already took care of when i first rebuilt the engine.

[Rybar]

thats a good idea, but something i already took care of when i first rebuilt the engine.

Well have you replaced your Opti spark? Trust me they are notorious for causing all sorts of problems like you are describing in both threads. I know they can be pricey but you have to deal with that for LT1's

You should install the 95+ vented style opti. 93-94's had non vented and when they get any kind of moisture or dirt inside they can cause havoc.

[69camarokid]

the opti is a the stock unit with about 130K miles on it so it could be going south. My is a 95 so its vented. But it is one of those things to do when i get money. which will be....
....someday. haha

[Rybar]

the opti is a the stock unit with about 130K miles on it so it could be going south. My is a 95 so its vented. But it is one of those things to do when i get money. which will be....
....someday. haha

With 130k miles I am sure its finished.