Revs Increase 400 Rpm When Clutch Is Pressed Or Cruising In Neutral

[Moberg]

Hello, I'm new to this forum, so my apologies if this issue has been discussed. I tried to search the forums, but did not find a precisely similar topic/problem.

I bought my used 2007 Corolla 1.6 about two months ago. It has a milage of approx 50000 miles. Manual gear.

The problem is that the revs seem to rise for about 400 rpm, if I press the clutch or change to neutral. Take for example in the morning - The engine is cold and the normal idle is 1000 rpm. When I am in normal drive at approx 1500 rpm and approach a red light, I depress the clutch (in intention to just cruise to the light before stopping) and my revs drop to normal idle and immediately climbs to 1400rpm. As soon as the car is completely stopped, the revs drop back to normal idle.

The same happens with a hot engine. Normal idle is approx 600, i drive at normal speed at 2000 rpm, depress the clutch and the revs drop first to 600 rpm and climb immediately up to 1000 rpm, where the revs hang until the car is stopped. It feels as like the ECU is forcing the engine to rev an additional 400 rpm.

I took it to my local Toyota dealer, who told me that it just might be normal behavior, which seemed quite stange to me. They agreed to change the air intake gasket and to clean my throttle body as warranty work, as I suspected an air leak or a dirty TB. I also did a ECU reset, but none of these had any effect.

Is this normal behavior or not. If it is normal, is it due to emission control or to burn out any excess fuel?

[MD1032]

No worries, mine does the same thing and I have the intake manifold gasket fix done. I think the ECU on this car is programmed to keep the engine in a certain state while moving to make the clutch engagement smoother or otherwise. Mine usually waits until a few seconds after a full stop to go into the low idle mode.

[invader]

It is normal. Engine speed is above normal idle when you're still moving for better brake and steering assist, and to reduce stalling tendency for increased safety.

Also, the ECU may momentarily keep the engine speed above idle when shifting out of fifth (or sixth XRS) gear at highway speeds. This condition occurs only briefly and only when the vehicle is in neutral. It's designed to prolong the life of the catalytic converter.

[invader]

Originally Posted by Moberg

I also did a ECU reset, but none of these had any effect.

It will take some amount of driving time for the ECU to relearn operating conditions... Idle quality and stability will improve, and may end up better than before the intake manifold gasket replacement and TB cleaning.