Can a bad IAC cause a vacuum leak?
An incorrect idle speed with the IAC unplugged (and a normal idle speed with the IAC connected) indicates the valve and its control circuit are working properly. There may be another problem, such as a vacuum leak causing your concern.
How do you test an IAC valve?
Here is how to test and clean the valve:
- 1) Open the hood of your vehicle.
- 2) Pull the electrical plug off the control valve.
- 3) Take out the idle control valve and flip it over.
- 4) Take your voltmeter and set it to “Ohms.”
What does a bad IAC valve look like?
When an idle control valve goes bad, the initial symptoms may be mild. At first, you may notice that the engine feels rough when you are sitting at a stop sign or traffic light. The car may also sound different when it is idling. A car with a bad IAC valve is more likely to stall in traffic when you are idling.
What does it mean when IAC valve is closed?
Considering a vacuum leak, a common condition is to find the IAC valve extended all the way out (closed position). This usually means the engine has an air leak and the engine computer is trying to bring the idle speed back down by closing the idle air bypass circuit.
How to clean the idle air control valve ( IAC )?
How To Clean The Idle Air Control Valve (IAC): One common problem is a buildup of carbon or fuel varnish deposits in the idle speed control valve. The cure for this condition is to clean the valve, with some aerosol throttle cleaner or engine top cleaner. Follow these common instructions: Disconnect the air intake ductwork from the throttle body.
What’s the best way to test an IAC valve?
Without a doubt, using an OEM-level scan tool is the easiest way to test an IAC valve. OEM-level means the scanner has most of the same functions as the dealer’s factory tool. Code readers and OBD-II scan tools don’t have the necessary bi-directional controls to test an IAC.
When to set a code for a bad IAC?
Then there’s probably a problem with the IAC, a vacuum leak, or a problem with the IAC control circuit. In most cases, cars built after 1996 with onboard diagnostics (OBD) II will set a code for a bad IAC. Many older cars with OBD I will also set a DTC when there’s a problem with the IAC.