Why does my RPM drop when sitting idle at traffic lights?

While I’m sitting idle at traffic lights I put the car into neutral. The engine stays idling at about 1000 RPM. However every now and then it drops down to about 500 RPM and then quickly back up to about 1200 then goes slowly down to 1000 and stays there for a bit until I go again or it drops again.

What should the engine RPM be at idle?

Come to a light and stop or just sitting in the drive way when warmed up. Car in drive and foot on brake. RPM about 650 down to 500 and slightly running rough. Take foot off brake (car is chocked so won’t move) and RPM back to 650-700 and no issue. Back on brake same thing.

What happens when engine RPM drops below 800?

However, when the engine RPM drops below the normal range of 800 RPM (for most cars), it is more than likely that you are dealing with an IAC valve problem. In cases where this valve is clogged or is failing, your vehicle will stall instead of slowing to an idle after the release of the throttle.

When do I stop at red light RPM drops?

But when i stop at light rpm drop to 500. And feels like its going to shit off. My car has 80455 miles. My car has an automatic transmission. This may be a sign of a failing idle air control valve.

While I’m sitting idle at traffic lights I put the car into neutral. The engine stays idling at about 1000 RPM. However every now and then it drops down to about 500 RPM and then quickly back up to about 1200 then goes slowly down to 1000 and stays there for a bit until I go again or it drops again.

Come to a light and stop or just sitting in the drive way when warmed up. Car in drive and foot on brake. RPM about 650 down to 500 and slightly running rough. Take foot off brake (car is chocked so won’t move) and RPM back to 650-700 and no issue. Back on brake same thing.

But when i stop at light rpm drop to 500. And feels like its going to shit off. My car has 80455 miles. My car has an automatic transmission. This may be a sign of a failing idle air control valve.

However, when the engine RPM drops below the normal range of 800 RPM (for most cars), it is more than likely that you are dealing with an IAC valve problem. In cases where this valve is clogged or is failing, your vehicle will stall instead of slowing to an idle after the release of the throttle.