in what order should all that be done so one doesn't skew another? i'm thinking timing, then IAC, then TPS?

 

Timing first, then throttle position (minimum air adjustment), then TPS voltage.

 

Incidentally. the TPS on a '90 or '91 may not be adjustable, so plan on setting the timing and minimum air. You have the procedure, right? You need to close down the IAC then remove its connector before adjusting the throttle minimum position.

BTW - Nice signature.

 

yea, TPS is adjustable. and yes, i have the procedures. thanks. did you mean the TPS when you were talking about adjusting the throttle minimum position? or was that in reference to setting the IAC? hopefully i can get to this tomorrow - right now my alarm system seems to be AFU. power door locks WON'T unlock except with the key fob. good thing i was home when i discovered that one. never did figure out the fuel pump cycling thing... but the grounding issue is fixed now.

 

I'm guessing you don't have the article on setting the idle. - put your little "code key"(paper clip) in and turn the key on. - wait about 30 sec and disconnect the IAc w/ the key still on. now start the car, put in gear(if auto) and adjust the set-screw for the butterflies. This is "minimum air position". Now adjust the TPS for proper voltage, and re-connect IAC. If you don't have anyone to sit in the car and hold the brake(in gear remember), lock the e-brake and put the rear up on jack stands. This isn't the safest way(nor do I accept resposibility for), but its the best way I know of.

 

actually, i did have all that, but thanks. ever hear the version of disconnecting the EST connector after the IAC connector prior to starting the engine? somebody wrote that and i still have it. if you don't, the ecm will try and adjust the timing... confirm or deny?

 

I've heard that, but wouldn't work for me. The TPi I've been working on is...different. It's in a 95 Tahoe, 355ci, ported vortec heads, 305 hyd roller cam w/ 1.6 roller rockers, ported plenum and base, stock 305 chip/injectors/ecm/etc...It won't idle at all w/ the EST disconnected.

 

The term "IAC adjustmnet" is a misnomer. There is no way to "set" or "adjust" the IAC. The IAC is under constant control of the ECM.

The procedure most people are trying to describe by that label is to park the IAC in the fully closed position, disable it, then adjust the minimum air position of the throttle plates to maintain a specified idle RPM. There is no "adjusting" the IAC. You can remove it, set the pintle in about any position you want, reinstall it, and it will move as soon as the ingition is turned on.

If you have an adjustable TPS, set that last. I wasn't sure what year the change was made to a fixed TPS. Must be about 1991.

 

If the engine will not idle without the EST active, you may need to reset the base timing a little higher for the cam you have installed, then set the minimum air position to support that setup, then the TPS.

The next thing you're going to need to do is program the ECM for your setup. Is it using a MAF?

 

When I re-did my IAC the book I was using (Chiltons, yeah I know) had a specific measurement to set the tip of the pintle from the flange. I think its was 26mm or 1.03 inches but I cant remember exactly. So while it was off you can rotate the pintle and change its distance from the flange. Then supposedly you put it back and no minimum idle adjustment was needed. To be honest I dont know if this was a bunch of fluff or if this actually works. In my situation it ended up being the IAC was not the cause of the problem, just faulty troubleshooting on my part. When I put this new distributor in (and hopefully the car works) I'll be able to verify if this 26mm or 1.03 inches thing makes any difference or if I need to run through the minimum idle procedure. On a side note, I keep fighting with my TPS, I get either .53 or .55 LOL no matter how many times I try I cant get .54 (even while watching the scantool and making small small adjustments).

 

10mV will make no difference. You're sweating over nothing. As long as it's in the range of 0.48 to 0.60V, it should be fine. 0.54V just happens to be the middle of the acceptable range.