GMC Repair: Idle Speed, air control valve, combustion chambers

Question
How can I raise the Idle Speed on my 2002 Gmc 5.3 Pick up?
It has no throttle cable, it has an electronic sending unit on the gas pedal.
Do not see any adjustments, It now Idles at 450RPM
which I feel is to low.

Answer
IF you have had ANY work performed on the vehicle of any kind, I need to know WHAT was done.

The most likely possibility is:

1. A fault in the IAC (Idle Air Control) valve.

2. A buildup of stick black residue within the idle air passages that normally builds up over time and requires cleaning of the idle circuit.

3. This same residue build-up around the throttle plate area of which would need to be cleaned.

4. Water in the fuel.

5. restriction in the air intake hoses (clogged air cleaner).

6. Leaking fuel injectors dripping fuel into the combustion chambers.

7. Low fuel pressure.

8. kinked, restricted or worn out vacuum lines.

9. TPS (throttle Positioning Sensor) set incorrectly or internal fault. Will NOT always turn on the CHECK ENGINE light on the dash panel inside the vehicle.

10. Faulty KNOCK SENSOR.

11. Incorrect ignition timing.


IF NO-ONE has been ADJUSTING things on the engine and there has been NO work performed on the vehicle of ANYKIND WHAT-SO-EVER, The most likely suspect would be :


1. Residue build-up and or IAC problems as said above.




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