Tripleblack90

When the car is running, the vacuum will hold it open and it will idle around 1500. If the car is not running, it returns fine. Engine vacuum, not a worn throttle blade, will hold it open. It is a new throttle body. I put springs on it that will help to overcome the problem but then you need a lead shoe to depress the accelerator pedal.
--I recently changed the motor, same problem
--I have unhooked the cables, same problem
--I have changed the coolant temp sensor, same problem
--I replaced the IAC, same problem
--I have replaced the throttle body, same problem
--I have replaced the TPS, same problem

Yesterday, I replaced the MAP sensor, unhooked the IAC and the TPS, turned the key to the "on" position for 3 minutes. Turned the key "off". Hooked the TPS and IAC back up. Started the car and it idled perfectly, drove it about 10 miles, perfect, idled down, perfect. I stopped and shut the car off, unhooked the one TB helper spring, (I was feeling good about it now) drove it a few more miles, perfect. Drove it another ten miles, IDLES HIGH UNTIL YOU KICK IT ONCE.. IT"S BACK...............

Tripleblack90

ttt

Square

Have you done a base idle reset?

What was the base idle running at?

turbopezz

Try setting the Iac and Tps using a volt meter.The aftermarket throttle body might need the tps ''clocked a little bit.
Look at A shop manual for the specs and procedure.

turbopezz

http://temp.corvetteforum.net/c4/vader86/baseidle.html

aklim

Do you have a scanner? I would set it off the IAC counts. Screw it in if the counts are high and screw it out if the counts are low. Aim for 15-20 counts. After that, set TPS if it is adjustable. Before all this is done, timing must be spot on.

Tripleblack90

Yes, a base idle reset was done.

The car idles, when normal around 800 rpm.

Tripleblack90

The TPS is non-adjustable. I have not been able to try setting the IAC with a voltmeter. I have had it to several shops, thrown $100 bills at it and am trying to figure this out on my own now.

Tripleblack90

I do not have a scanner. I would like to be able to figure out the IAC counts.....

This is a throttle body from xtreme-fi. My concern is that it even has the right IAC valve. There is a difference between one for an 88 and one for a 90 even though the look the same. Without ordering another new one, I do not remember which valve is in the car. They look the same.....

aklim

Yes but that means little. We don't know what the command idle is. Do you know what the ECM program is trying to set the idle at? That seems a little high for a stock ECM

aklim

You need a scanner to read what the ECM is seeing.

Tripleblack90

Replaced the ECM. Reset the base idle. Took it for a 1/2 hour drive. Life seems goods again..............This has been very frustrating.
As I side note, while resetting the base idle, trying to unhook the EST wire, I think I un-hooked the right one. The tach does not work when it is unhooked. Oh well, the car is running good again. It is hard to drive keeping your fingers crossed.

aklim

Sounds like the wrong one. It should be a tan single wire. Tach works with or without that thing connected. All it does is give the distributor a signal to advance timing.

Tripleblack90

I think it was a single tan wire. Not sure which one else it could be.

aklim

Then I don't know why your tach stopped working. Did the timing go back to 6 deg?

Tripleblack90

I do not have a timing gun. I do know that it runs well now

aklim

I had some ******** set my timing to 19 deg and the car ran well. Thing was that the PCM was backing timing down and other things to compensate.

Tripleblack90

The guy that put the motor in set it at 4, or so he said. I have had 3 places look at it, couldn't fix it. Finally put a post on here and learned to do it myself.
I used to work on my stuff all of the time. Got to that point in my life that I would prefer to pay someone to work on it for me. Unfortunately, competent mechanics that are familiar with older vettes are few and far between. I decided to get my hands dirty and fix it myself.......now I know why I prefer to have someone else work on stuff.......

aklim

That is wrong right there. It should be set a 6.

Tripleblack90

Now do you see why I end up working on things myself........