Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Hello & Welcome,
The idle speed on your vehicle & engine is controlled by the Idle Air Control (IAC) valve, which is controlled by the Powertrain Control Module. So there is no external adjustment, like there used to be on older engines that had carburetors.
What will often cause a poor idle condition is deposits (dirt) inside the throttle body. This will cause bad air flow through the system, and especially near the IAC valve.
What I would do is give the throttle body a good cleaning with carburetor cleaner (as a start). This will remove the deposits and allow the air to flow properly through that part of the system.
I have included the following PDF file about replacing the IAC valve to show you where it is and where to look. I have also included the Idle Relearn procedure, just in case you need it. You should be able to click on the links and view these files on your computer and print them out, if needed.
Replace IAC Valve
Please let me know how it goes or if you have more questions.
Take Care, Greg A.
need help on a 1999 Chevy K3500 pickup with a 7.4 L