Hello I need some help 89 lo3 sometimes idle is 600 sometime 1000 I thought the tbi unit gaskets may be leaking so I took off and grinded off the ridge like in the ultimate tbi mods and replaced all gaskets after I set the min air and tps the idle was perfect test drove and was back to 1000 I'm park 750 In gear can hear tbi sticking when moving by hand with no cables hooked up but I can't see where its sticking please help

 

Try adjusting your minimum idle screw so that the throttle plates front edge does not come in direct contact with bore surface. The gap between plates and bore will be less than hair thin, but this will prevent from sticky throttle syndrome. As you adjust minimum idle screw keep an eye on IAC counts - as you adjust do not go below 15 to 10 counts.

//RF

 

Thanks I'm going to try that I have a tech 1 so just as long as the iac count don't drop below 10 te idle will still be right

 

I was having this problem as well after installing an RV Morse throttle body. It would idle high, but if i hit the throttle quick, it would close properly. I ended up putting a carb throttle return spring on. Made the pedal stiffer (which I personally like) and stopped the issue.

 

I have one of his 47mm reworked SBC TB with exactly the same symptoms (on of my engine builds). He is local to me, so I may have to pay him visit. It does look that an adjustment of the minimum idle screw takes care of this unstable idle condition. I'll verify to be certain, by backing it off and setting it again.

//RF

 

I've already got it adjusted to where the IAC registers 5-10 steps at warm idle, so I don't think I really wanna open the throttle blades any more than they already are.

 

So turn the min idle screw until the throttle plates just open? Wouldn't this cause high idle or will the iac adjust idle to 600 in gear

 

There is a specific procedure to set min idle. I am sure it is here somewhere.

IAC steps can increase idle as well as lower it assuming the throttle blade is not open too far. IAC pindle set to 10 steps allows it to close 10 steps to reduce idle. If TB is open to far it will move to 0 steps and idle could be too high. I am at 5 steps and occasionally I see 0 steps and idle RPM is still OK.

 

Thanks for the info guys yeah I reset tps and adj min air when I first got the car like 2 months ago. Previous owner had it out of whack because car wouldn't idle in gear after a hour of diag I found dissy rusted and pick up coil bad replaced the dissy and ran perfect beside idle was iratic. I completed the procedure again after completing ultimate tbi mods. Must of did something wrong I was in a hurry at lunch and was tieing up my flat stall. Readjusted today and idles great all the time. Now it's time for some mods thinking some 3.42 gears and working on rear suspension then rebuilding trans with a shift kit