Here is one for you all. My 87 has started to act up. It will idle 500-600 RPM cold and stumble. As it warms up the idle increases. When fully warm it idles 1600. I have check and repaired vacuum leaks. It was intermitent for a while. If I disconnected the battery to clear the ECM it would be fine,now it is all the time. Idle Air Motor?

Could be the IAC valve sticking/carboned up. If the throttle body and IAC have not been cleaned recently try that. When the engine is warm and at "high idle condition" try tapping on the IAC lightly w/handle  of a screwdriver to see if idle comes down and/or engine shuts off-- if so a sticking IAC is likely the culprit. A bad TPS can also cause your problem, but I'd check the IAC  and be sure it's clean first.

Thanks, I will check that when it warms up. Brrrr it's cold out!

with computers it is hard to pinpoint sometimes. check as 96lt but this happened to a friend of mine. he changed the iac and the tps and trouble kept up. in a local shop the owner which is a frioend of his told him to replace the temp sensor which is between the 6 & 8 plug. said that a customer spent a lot of money on a vette and was going to get rid of it and it cleared his problem. he tried that and cleared up but came back. he finally replaced the computer and it cleared up all his problems. with all these systems intergrated sometimes it can be hard to determine what exactly it is. hope this helps. btw...he has an 88.

I would also suspect the IAC motor, OR carboned throttle body/blades. You can get a throttle body spray cleaner at most parts houses. Regular carb cleaner spray can sometimes damage the coating on the throttle blades, and the IAC, if it get into it. I would suggest a thorough cleaning first, then drive it a while to get the idle re-learned, and see how that works. If cleaning does nothing, then the IAC may well be so gunked up it just can't operate properly.
If you have access to a scanner, the scan data would help point you in the right direction.

[QUOTE=Adams' Apple]I would also suspect the IAC motor, OR carboned throttle body/blades. You can get a throttle body spray cleaner at most parts houses. Regular carb cleaner spray can sometimes damage the coating on the throttle blades, and the IAC, if it get into it. I would suggest a thorough cleaning first, then drive it a while to get the idle re-learned, and see how that works. If cleaning does nothing, then the IAC may well be so gunked up it just can't operate properly.
If you have access to a scanner, the scan data would help point you in the right direction.
[/QUOTE]


Boy this is overlooked a lot!!


Besides the cost of a few cleaners, keeping the complete air induction and emission components clean is so vital to performance and a smooth running engine.

Here is a thread I made a few months back about proven results of cleaning the MAFS...the air induction tubes and TB blades were cleaned as well.

GOT 42hp BACK BY CLEANING THE MAFS

These are DYNO results.
It was just simple neglect...the stuff got dirty faster than I thought, but the cars computer told the dyno computer how well the engine ran a few months back.
My friend remembered too (the dyno guy).

Point is; its FREE to keep all components cleaned and in good working order.

FREE:
*******All sensor wire connections clean and in place.
*******Air induction unit clean all the way up to the first gasket that would require changing.
*******Free to brush spark plug electrodes and re-gap correctly if needed.
*******Free to remove spark plug wires and clean contacts (add die-electric grease if available)
*******Inspect all vacuum hoses, clip old ends, re-connect ends....this especially includes vacuum T's, 90's, and trees....you'd be surprised how many are cracked or broke, and not visible unless carefully inspected...several are hidden under looming, other under plastic components, ect...



There can be so many things to look at when diagnosing....without a lot of high dollar scanners/equipment what makes it easy; is if you eliminate a huge portion of components by knowing they are in good working order.......sometimes its that knowing of "whats NOT wrong"
pinpoints the fault, or the "path to the fault".

 

When it cold you can go check a couple of things; then go back in the house. 




GL
Jim

 

I had the same problem,cleaned the t-body with the engine off & added a can of Seafoam to the gas tank.So far it solved it.

Thanks guys , you gave me some homework to do when it warms up some here. I can't stand the cold anymore. I grew up in upstate NY where it is COLD ,I left there to get away from it.