I need help!!! New TB!! Bad Idle!!!!!!

[fourmustangs]

I just put a throttle body on my 87 5.0 with AOD.
It was running great then next thing I know My rpms are staying 3000-4000 rpm.
It now is at 1600 rpm at idle and because of the idle the shifting is just a little off.

Adjusting the idle screw is n/a it ran good just before.
the tps is good has the right voltage.

I have checked the codes and not a single code....all ok

let me know what you think cause I dont know.

ps. I've checked almost all vacuum ports no problems in engine bay.

 

[troyGT03]

unplug the iac, then adjust the idle screw and tps(as close but not 1volt DC as possible) to get a idle @ 900(auto). it will run a bit rough but will idle if no vac leaks. then plug the the iac in. jricker and hissin50 will give you the better explanation. i gave you the cliffs notes.

 

[fourmustangs]

Thats how I set it and rechecked the voltage once the problem hit

 

[HISSIN50]

Are you really sure the throttle blade is not sticking (this is an issue with some aftermarket TB's)? The throttle linkage is not able to get stuck or hung up?

If one desired, you could run wiring from the TPS signal-return to your DMM and put the meter in your car - that way you can monitor TPS readings in real time (best to have an assitant, etc do that, so it is not a distraction).

Here is an article on resetting the idle (you have gone over it I am sure, but redundancy when trying to find a solution doesnt hurt).

Good luck.

 

[fourmustangs]

It wasnt stuck it has free play.

When it was running right itwas about 950 rpms
I got on it a few times and was going to the strip and on the way there and when I was there it acts like the throttle is stuck open when its not.

 

[jrichker]

An idle that goes high and stays high until you shut off the engine is a sign of a bad TPS.


Wire colors & functions:
Orange/white = 5 volt VREF from the computer
Dark Green/lt green = TPS output to computer
Black/white = Signal ground from computer

Check the orange/white wire for 5 volts.

Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter.
Check the resistance betwee the black/white wire on the TPS and the negative battery post. You should see less than 1.5 ohms.

 

[fourmustangs]

Changed TPS and made couple adjustments and it idles at 1000.
any lower it starts to surge.

seems to be running good now

 

[jrichker]

Changed TPS and made couple adjustments and it idles at 1000.
any lower it starts to surge.

seems to be running good now

See the sticky "Help me create the Surging Idle Checklist" at the top of the forum for help with your idle problems. The first post in the sticky has almost all the details you need.