TBI idle and IAC steps

[chris989]

Hello,

I have a 89 5.7 auto suburban 4x4.  I am using moates auto prom and data logging with Tuner pro.

Problem:  I can get my idle to go below 875 with zero IAC steps.  I am attempting to correct the idle with a new bin but can not get it ironed out.    I do notice that the data log always show i am in park,  even when i put it in gear,

Question.  Tunerpro is for many vehicles, (more sophisticated than my 89).  Does anyone know if my aldl should register park all the time or is my wire broke somewhere in my steering column causing my truck to always attempt to maintain idle speeds relative to park/neutral??

Thanks,
Chris

[bake74]

     Well Chris, I do not have the answer's for you.  But I wanted to welcome you to the site, and be patient, someone will see this and reply.  Probably not until Wed. though.

[rsandusky]

Welcome Chris!!

First verify that you don't have any vacuum leaks. Vacuum leaks will cause a lean condition that is picked up by the oxygen sensor, the ecm then adds fuel to correct for the lean condition.

http://forum.73-87chevytrucks.com/smforum/index.php/topic,21039.0.html

[Captkaos]

Did you find an answer to this?

[VileZambonie]

There is no transmission range switch. Check for vacuum leaks/tbi base gasket.

[frotosride]

Your issue with the IAC is because as I'm sure you know, inorder to set up IAC properly you have to have the butterfly's completly shut....and TBI's don't have an adjustment screw...or do they. If you notice on the throttle body there is a plug, I do believe on the left side. drill this out and you can adjust the butterfly's as you so desire.

[VileZambonie]

Your issue with the IAC is because as I'm sure you know, inorder to set up IAC properly you have to have the butterfly's completly shut....and TBI's don't have an adjustment screw...or do they. If you notice on the throttle body there is a plug, I do believe on the left side. drill this out and you can adjust the butterfly's as you so desire.

Do not mess with the screw - all you'll be doing is creating another reason to start chasing your tail. Fix the problem not the symptom.

[frotosride]

Your issue with the IAC is because as I'm sure you know, inorder to set up IAC properly you have to have the butterfly's completly shut....and TBI's don't have an adjustment screw...or do they. If you notice on the throttle body there is a plug, I do believe on the left side. drill this out and you can adjust the butterfly's as you so desire.

Do not mess with the screw - all you'll be doing is creating another reason to start chasing your tail. Fix the problem not the symptom.

+1Very good point...maybe i should learn to read better before i reply to threads. I don't know why I was thinking that He was trying to get a newly preped engine running correctly when i replyed to this. But erase the screw from your memory or you will likely be chasing a new symptom....Thanks for the catch "Vile"

[DnStClr]

My memory escapes me about the size of the socket you need to remove the iac unit- is it 1 1/8"? anyway- while you're checking for vacuum leaks, it's easy enough to take the iac out and give it a good cleaning with throttle body cleaner spray..

[DnStClr]

If you want to see what your ecm is doing, you can download a free program called winALDL-
http://winaldl.joby.se/
but you'd need to spend a few bucks to make up a small cable.