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