1994 k1500 z71 idle help

[klowninc89]

Hi i done a lot to this truck. I replaced plugs wires iac valve egr valve egr valve cylinoideand few vacume lines. It still has a low idle idk whats wrong driving its good. But just in gear has low idle at like 500-400 rpm. Any ideas?

 

[Z71paramedic]

Is it throwing any codes? My 93 idles at about 600 in gear, so you're not far off. Is it stalling?

My guess is possibly TPS or maybe the MAP. If it's stalling it may be the ICM.

 

[klowninc89]

No engine light o i have not replace map sensor yet but not throwing any codes. Even when ac is on does not seem to idle up. Icm? Idk run great other than that.

 

[Z71paramedic]

If it's not giving you trouble I wouldn't mess with it to be honest. 400 is too low, but 500-600 is pretty normal.

ICM is ignition control module, located on the base of the distributor under the cap.

Don't forget, this is OBD1, so it's unlikely that it will turn the light on and stay on unless something bad is going on. You may want to flash it and see what codes it has stored if any.

 

[British Slave]

Don't you adjust idle speed on the 94 the same as 87?

 

[Z71paramedic]

Don't you adjust idle speed on the 94 the same as 87?

yeah, 87-94 were all the same TBI. Is there an adjustment screw? I can't remember because I haven't seen it in 3 years

 

[British Slave]

Idle Speed Adjustment​

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 the paper clip.
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.
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.

 

[British Slave]

The idle adjustment screw is located on the lower right front of the TBI.