1987 Chevrolet 350 tbi high idle

[iamtherealJayy]

Also, note the engine started with just a “bump of the key” after cleaning iac, sadly I suppose that’s just carb cleaner than had got in the throttle body when spraying the iac hole.

 

[iamtherealJayy]

Well scratch the idea of using the Ir thermometer tonight. I found it changed batteries and nothin wouldn’t do a dang thing. Spent a half hour cleaning it up and messing with it and still nothing. Reckon tomorrow I’m gonna try to get a new one and continue the testing.

 

[gmbellew]

now that you have cleaned the IAC. try the reset procedure again. the ECM needs to know where it is....it is not smart enough to figure it out.

 

[iamtherealJayy]

Is the reset procedure what you’d sent previously? I can go back and read up I can’t remember how exactly to do it.

 

[iamtherealJayy]

Just disconnect the battery turn headlights on and wait a bit? Reconnect and start engine?

 

[gmbellew]

I think it is key on for 5 sec. off for 10 sec. then start the truck

 

[AuroraGirl]

@AuroraGirl I have an ALDL scan tool on the way, should be here any day now and then I’ll be monitoring live data. I read everything you just sent. I’ll get to work on testing what I can.

But you dont really need the live data for any of this diagnosis its just.. convenient. but even then, its only telling you what the ECM sees and processes assuming its undamaged or has no faults internally that you or I dont technically no lol.its a lot easier to measure voltages and use a chart to see what the sensors are saying. there arent many

Also your IAC appears to have suffered damage from bottoming out or being the wrong pintle. That has inteference wear not abrasive contaminents hitting it wear

 

[iamtherealJayy]

Alright I just disconnected the battery, I’m going to wait a minute reconnect it and start the truck. Then try key on 5 key off 10 start and observe results.

 

[iamtherealJayy]

@AuroraGirl the iac does appear to have a “wear” ring around it close to the bottom of the point I just assume it was where it touches so it stayed clean. I can work on getting a new one tomorrow?

 

[gmbellew]

if that doesn't bring idle down. go back and read how to force the iac to close all the way and then start truck and see where it idles. if it doesnt drop down, I'd also pull the iac before plugging it back in and see how far it is extended...the IAC could still be bad even though it is now cleaner.

 

[iamtherealJayy]

After reconnecting the battery and doing the ignition on 5 off 10 start it sat at ~1700 came down to roughly 1000 and has sat there for a few seconds now. The truck started shaking a little when it came down to 1000 but it has since smoothed out.

 

[AuroraGirl]

After reconnecting the battery and doing the ignition on 5 off 10 start it sat at ~1700 came down to roughly 1000 and has sat there for a few seconds now. The truck started shaking a little when it came down to 1000 but it has since smoothed out.

1000 is a good warm up RPM after the intitial "kick" down from 1500 or so

 

[iamtherealJayy]

I hit the gas pedal and revved to around 1800 it came back down to around 1100 and has now increased to 1250 ish

 

[iamtherealJayy]

Forced iac closed I could hear it clicking(assuming stuck? Not closing all the way?) unplugged it started truck and did same thing as before started with 1600 came down to around 1100 and stayed there for a bit.

 

[gmbellew]

If it were me, I'd buy a new Delphi IAC, make sure the IAC passage is clean when I put it in, reset it, and be OK unless you have other vacuum leaks.

if you want to wait on the part and not spend the $50 at partsgeek, I'd check the IAC counts with your ALDL cable when it shows up to make sure the IAC is bad before spending the money.

if your cap is still on the idle adjustment screw, it probably is NOT the issue. there could be butterfly issues in the TB I suppose?