Rick's Free Auto Repair Advice

Posts Tagged: idle air control valve

Idle air control valve

What is an Idle air control valve? An idle air control valve (IAC) is usually mounted to the throttle body in a fuel injected engine. The valve opens and closes based on commands from the vehicle’s powertrain control module (PCM) to provide a specified amount of air needed to keep the engine running during idle. Types of idle air control valves IAC valves are operated by a stepper motor, servo motor or electric solenoid. The motors move a tapered pintle into or out of a matching tapered seat, thus varying … Read More

How does an idle air control valve work

What is an idle air control valve Many people are confused about how idle air control valves work. An idle air control valve literally bypasses air around a closed throttle plate so the engine can get air at idle. Because it bypasses air, it’s also called an air bypass valve. Back in the days of carburetors, idle speed was adjusted by way of an idle speed screw. In fact, on many carburetors there were two idle speed adjustment screws; one for hot idle and another for cold. Turning the screw … Read More

Bad idle air control valve

Bad idle air control valve symptoms Idle speed goes up and down or high idle First off, this is a fairly common problem for all makes and models. Sometimes the problem is caused by a gummed up or sticking idle air control valve (IAC) or a dirty mass airflow sensor (MAF). But it can also be caused by a vacuum leak. How an idle air control valve works If you’re familiar with older carbureted cars you remember that you turned a screw to set the idle speed. The screw turned … Read More

P0505 P1505 P1129 surging idle CRV

Fix code P0505 P1505 P1129 surging idle Honda CRV If you have P0505 P1505 P1129 surging idle Honda CRV  you may have a bum idle air control valve (IAC). Here’s how to check. First, make sure the coolant level is full and that the cooling line running to the IAC is hot. If the line isn’t hot but the engine is, the line is blocked. Clear it before proceeding. Next, cover the throttle body while the engine is running. The engine should stall. If it doesn’t, you have a vacuum leak … Read More


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