kirkcomer

I've been using this how-to article on the couple tpi f-bodys I've worked on. Great instructions but I "think" I've added one more important instruction(see bold type below) and I also have a question that I know someone can surely answer for me(see bold type below).

IAC and TPS Adjustment
Idle Air Control
Tools needed:

Torx bit # T-20
Paper Clip
Small Punch

Take the paper clip and open it up and form it into a big "U" shape. Insert the clip ends into the ALDL in the ‘A’ and ‘B’ pins.

Turn on the ignition, but don’t start the engine. Wait 30 seconds. Now, go remove the connector from the IAC.

Remove paper clip from 'A' and 'B' pins.

Start engine. You are now going to adjust "minimum air". There is a Torx screw on the side of the throttle body. This is what needs to be turned to adjust minimum air, or more commonly known as "idle speed". It comes from the factory with a protective metal cap over it. If the cap is still there, use a small punch to knock it out. Set the idle speed to 450 rpm, rotating the Torx screw clockwise to raise rpm, and counter-clockwise to lower rpm. Once the idle rpm is set, turn off the engine. (Should I set the idle speed while in drive or park??... I've been setting idle speed while in drive.)

Re-connect the connector onto the IAC. Start engine. Idle speed is now once again governed by the ECM, but your idle should be smooth and steady, approximately 600 rpm in Drive (for unmodified cars).

If you set an SES light by having the IAC disconnected, then after shutting down the engine disconnect the negative battery terminal. Wait 5 minutes. This will clear the ECM of all trouble codes. Re-connect the battery and drive the car for 20 minutes to allow the ECM to relearn your driving style.

Ron U.S.M.C.

In park at operating temperature.
There is a "very" thin clear plastic coating and is hard to see on most paper clips. It must be removed or it will be a very long day, indeed.

My car is a "89" 5.0 Automatic and min. idle speed is 700rpm. in "park" at operating temperature. Also any hose that's removed from any vacuum port must be caped off at the port.

Here's how I do it. Exactly like this.

"Setting Minimum Idle Speed"
1) Jump the A to B terminal under the dash.
2) Turn the key on but do not start it.
3) What 45 seconds,you should hear a slight ticking coming from the IACV.
4) Then unplug the IACV with the ignition still on.
5) Disconnect the EST wire and remove the jumper.
6) Start the car.
7) It may be necessary to hold the throttle open slightly to prevent the engine from stalling.
8) Allow the engine to reach normal operating temperature.
9) Connect a tachometer. I used a digital timing gun with RPM feature.
10) Adjust the minimum idle speed using the throttle stop screw.
11) My Chilton’s says set it to 700rpm in park on an 89 TBI 5.0 auto.
12) When done shut the car off and reconnect the EST wire.
13) Plug the IACV back in.

Drive the car easily at first allowing the ECM time to learn the new parameters.

Also, I have my car set to the stock "0" degree mark with "base" timing. You might want to set yours to "stock" for this procedure. What ever that might be for you.
You need at the very least a "Chilton Manual" for your car. $25.00 at any auto-parts store.

Setting "Base" Timing =
Disconnect the EST wire, start car and idle until the car is at operating temp., adjust timing, shut off car , reconnect EST wire.

kirkcomer

Thanks for the reply. I have been setting the min idle rpm to 450 while in park so good to hesr Im hopefully doing that okay.

​ I have not heard of unplugging the EST for this procedure before. I do unplug the EST to set my timing to 6 degrees.

i also let my engine be at operating temp when setting timing and min idle speed.

Ron U.S.M.C.

I had to set my min idle speed to pass smog . 700 rpm and "0" degree's is what he was looking for on my car.
That procedure is the only way I could do it.

kirkcomer

Thanks Ron. Good stuff. I have been reading up on this... popular subject.lol I'm glad you pointed out the timing. Definitely important. And the TPS setting is important as well.

The only thing I kinda question right now is what the minimum idle should be set at. I have mine set at 400 rpm in drive but I've seen people say to set this at 600 rpm in drive as well for a automatic. I "think" as long as the IACV is within the 20-50 step range it doesn't really matter but I'm gonna mess around with the rpms both ways to see what my scanner shows.

I think this is my "settings cheat sheet" (always subject to change)

“TPI 5.7 Automatic Settings”
1) Warm up vehicle to operating temperature.
2) Unplug EST.
3) Set timing to 6 degrees with car in Park.
4) Turn off car.
5) Jump the A to B terminal under the dash.
6) Turn the key on but do not start it.
7) Wait 45 seconds, you should hear a slight ticking coming from the IACV.
8) Then unplug the IACV with the ignition still on.
9) Remove the A to B jumper.
10) Start the car.
11) It may be necessary to hold the throttle open slightly to prevent the engine from stalling.
12) Allow the engine to reach normal operating temperature.
13) Connect a tachometer. I used a digital timing gun with RPM feature.
14) Adjust the minimum idle speed using the throttle stop screw.
15) Set minimum idle speed to 400 with car in Drive.
16) When done shut the car off and reconnect the EST wire.
17) Plug the IACV back in.
18) Turn the key on but do not start it.
19) Using scanner or voltmeter set TPS switch to .54
20) Turn key off.
21) Remove negative battery cable for 5 minutes.
22) Drive the car for 30 minutes easily at first allowing the ECM time to learn the new parameters.
23) Use scanner to check IACV reading in Park. Should be between 20 and 50 steps.
24) Use scanner to check BLM reading in Park. Should be around 128.
25) Turn of engine... settings complete.

Ron U.S.M.C.

The guy at my SMOG Station is really Cool. Ive been going there for many years.

Anyway, at operating temperature he puts the car in "Park" disconnects the EST wire, and looks for, 0* on the timing mark and 700rpm at idle.

Sooo, that's how I set it.
And that's how I was taught to do it.

I shut down one of my fans to reach 210*/220* mark after it idles for a while when I'm there.
Other wise, with a 180* thermostat and both fans it stays in the 180* to 190* range.

Since the stock air assembly is reinstalled for the test, when making the adjustments I set it off to the side a little so I can get to the IACV and still leave the vacuum line attached to the air sensor with in the assembly.
Believe it or not it does make a difference.