I have no fast idle and for the life of me I can't figure out why. It started after I tore the motor down to replace intake gaskets, add a holley regulator, and remove the air pump.

No vacuum leaks and the car runs rich at idle. I have checked the IAC and it moves, the passage is perfectly clean, I have reset the IAC and TPS. Nothing works and I don't know what to do. I have read every thread on the subject.

The car barely stays running in the morning or after it sits for a while until it warms up then everything is fine. Turning the idle screw makes it ok in the morning, but then when it warms up it idles to high. If you have any advice I would GREATLY appreciate it!

 

Your IAC is working, at 650 rpm it is trying to increase the air (160 counts) and is at the ECM limit.

The only way to lower the IAC counts is to increase the air some other way, opening the TB blades is one such way.

Or maybe your are too rich/lean, spark could be off (more advance can increase the idle speed).

You will have to change one thing at a time to see what makes it worse or better, follow what the motor wants not what you think it will wants.

 

Where do you suggest I start?

Some data logging shows the actual RPMs are not matching the requested rpms. The car is also idling a good bit rich.

 

Did you use RTV to seal the intake? If not correct type you could have killed the O2.

If not then how about a data log showing the idle? Cold and Hot.

 

I used permatex on the china walls, around the water jackets, and on the thermostat housing. Everything else was just paper gasket and metal. Here is the picture of it.

 

Well I solved the problem. I took the plenum and the SLP runners back off to trace the IAC ports and make sure there was no blockage. I found these wonderful plugs, in my driver's side runner, that completely blocked off the iac air flow.

Removed them and now everything works great!

 

Who would have ever thought of that?

My guess, looking back, would be "they" had an air leak which you "fixed". "they" fixed it by plugging IAC, which is just a controlled air leak. So you had to unfix "their" fix.

I have worked behind many other maintenance men, fixing CNC machines, these type of repairs are hard to find because, people can get very creative in their fixes.

Unwrapping some of these "repairs" takes as much understanding of the people involved as well as the machine.

This is why it is suggested to, after a while of tuning, to reload the original stock bin and start over. You can do this to your self, and it is very hard to remember or find, what is causing the issue your trying to fix.

Also after tuning for a while, things look different then when you first start out.

After 30 some years of repairing and tuning machines, there is always something "new" to learn.

 

No kidding... When I saw those plugs I was like YES and did a little victory dance. I think they come standard with slp runners though and the person might have used them with a corvette. Not sure though.


Anyhow, thanks again for the help!!