Huge short term positive fuel amount corrections during idle
 

Hi

I can see that during idle there are big (+25% .. +30%) short term fuel injection corrections. During driving there are no positive neither negative corrections. Oxygen sensors checked, no any air leaking. Everything seems to be correct except these positive corrections (both banks) during idle.
So it looks during idle there is too much air in the system.

Do you know any idle valve or something like that to correct it and limit amount of the air taken?

Regards, Marcin

Sounds like a vacuum leak or EGR malfunction. You don't say what year Blazer you have. Does it run poorly at idle?

You can see my Blazer data in the signature - year 2000. Idle runs smoothly, no egr errors, leaks were checked and tested. In another car I have there is possibility to adjust amount of air during iddle with special valve but here I can not see anything similiar.

What leaks were tested and checked? High positive trims at idle that resolve at higher RPM's is classic vacuum leak. The excess air becomes less significant as the total air volume increases.

Does it idle any differently before and after open/closed loop as its warming up?

What is happening with the total of short and long term trims?

George

Idle underpressure on the scanner is 0.35 bar what is correct and shows no leak.
I wonder if it could be IAC failure?