Basic tune question

[TOOMANYTOYS]

After replacing some parts and doing a tuneup on my 87 I’m having a problem getting the base settings to stay. I was able to get the tps to .42 but after setting the iac to 49 it has been steadily rising back up after driving it a few times. Checked it today and it’s up to 61 now. Driving around watching the scan master and the numbers go up very slowly. Around one count every 10-15 minutes. I only have about one thread left showing on the adjustment screw. What gives? How do I get this back into the proper range?

Mods are
60lb inj with TT chip and 340 pump
3” dp with pypes dual exh
RJC power plate
ESP fmic
LS1 maf with translator
F body alum rad

 

[earlbrown]

Why did you set the IAC at 49?

If you're having to open the throttle blade over and over, has the idle started going higher than the chip setting?

 

[dank GN]

To lower the IAC you will want to open the throttle blade . So open it till u see the IAC hold stead around 10-15 then re set the tps by loosening the screws that hold it to the throttle body and set it to .42 .

 

[TOOMANYTOYS]

49 was the lowest I could get it and the idle still held steady. I will try to reset it again and see what happens

 

[Pronto]

Back up, what parts did you replace?

 

[TOOMANYTOYS]

The ones I swapped are
Radiator and water pump
Steering box and solid shaft
Downpipe and exhaust
Power plate
RJC boost control
340 lph fuel pump
ESP fmic
Everything else was there when I bought it

 

[Pronto]

Powerplate. Check for a vacuum leak on the upper plenum. It's easy to strip the bolts...

 

[Chuck Leeper]

^^^^ This. Shoot some start fluid under the throttle body, at the ft edge of the plenum. A common place for a leak, as there's no bolts there.

 

[Jerryl]

A manifold vacuum leak will lower the IAC count. If the IAC is climbing, or you are unable to get them down, there is something else going on.

Post hot idle scan master oreally PL data with the fan/AC on for further review.

 

[Jerryl]

Going to turn off autocorrect on my phone.

 

[TOOMANYTOYS]

Yes the iac counts keep rising slowly. Also the warmer the car gets the rougher it runs at idle. The car is fine under throttle. From cruising to wot the car runs great with no kr

 

[earlbrown]

Might be ignition related then.


and the ECM is throwing stuff out of whack trying to 'tune' around a problem.

 

[bison]

Make sure throttle blade is not loose


Sent from my iPhone using Tapatalk

 

[TOOMANYTOYS]

I will check that. Thanks