I have a 89 vette that the idle speed drift up and down, I had a dealer do a computer check and it shows no problems. IT does this after the engine reaches operating temp.

Check the fuel pressure and check for vacuum leaks. Also, if it's MAF, check for leaking air between the MAF sensor and the TB.

You may be seeing the effect of an A/C compressor clutch cycling on and off. Does your engine speed change when the A/C is turned off? Or just when the A/C is on? If it's only happening when the A/C is on, then that's what's causing it.

I know alot about up and down but has nothing to do with cars:beerbang:

Faulty IAC or IAC ports clogged

It dont mater if AC is on or not, It does it after reaching operating Temp. It has a slight miss fire at higher RPMs and Eratic Idle. Here is all that I have done so far. Change Distr. Cap, Rotor, Plugs and wires.

Check the items listed in post #2 and #5 and report back w/your findings. We'll get it sorted out with you! :)

84/85; Is post #4 your idea of staying on topic??

Check the items listed in post #2 and #5 and report back w/your findings. We'll get it sorted out with you! :)

84/85; Is post #4 your idea of staying on topic??

I doubt he actually has any idea (other than mis-information, really stupid remarks, and childish insults).

I just want to post with the cool kids:2ni19wj:

I just want to post with the cool kids:2ni19wj:

Cool kids get time-outs too!:thumbsup3:

I changed the O2 sensor and fuel filter last night, The rich fuel smell went away, Still idle speed goes from 600 to 700. I also took the Mass Air Flow sensor off and cleaned still no change. I guess the Throtle sensor is next. Or even the EGR valve. No Vacum leaks have been found either.

Why did you change those parts? What tests have you run? Why do you suspect the TPS or the EGR? Are you following the advice given? Or just throwing parts at it?

It's hard to help if you don't take the advice given, and go do something different w/o an explaination. Good luck getting it running right.

-Tom

I changed the O2 sensor and fuel filter last night, The rich fuel smell went away, Still idle speed goes from 600 to 700. I also took the Mass Air Flow sensor off and cleaned still no change. I guess the Throtle sensor is next. Or even the EGR valve. No Vacum leaks have been found either.

Aahhh, you probably needed that stuff changed anyway, you will have it running better than ever soon and be really happy. Don't listen to captain tommy bring down.

Some of those items such as the O2 sensor, plugs and wire needed to be changed. I bought the car a year ago and no telling when they had been changed last. Some of the items were changed because of a friend that is a vette lover and he sugjested some of the changes. I guess that I am at the process of elimination right now.

Well after replacing all of the items I list previously, nothing changed. Now I see other things going on that I wonder may be some of the problem. Last night I took it out for a drive, As I drove I noticed that the dash lights were blinking on and off, and then I noticed the volts were at 12.2. I just replaced the alt. 2 weeks ago. Could I have a short or bad voltage

Have you had the intake runner off lately? The gaskets between the runner and the plenum. There,s a left and a right gasket they look almost the some, But if installed backwards there will be a vacuum leak on the drivers side and its hard to hear or to find but it,s there. A idle problem is what you end up with. If there,s a little part of the gasket sticking up 1/16 inch on one side only near the throttle body (cant remember witch side) there backwards.
David Steele

You may have a failing IAC motor.............

I have never taken the intake off, but that dosnt mean that some one else hasnt. I did replace the IAC motor and the Idle did smooth out. I do believe that I may have an injector that may be sticking open, the reason I believe this is after a while of runing it feels and smell as if it is loading up on fuel. When I ask for power it is not there. It has great power til certian RPM range.