Oxygen sensor and high speed stumble UPDATE

[Greg Hermann]

Hi--

Good accurate info, in general.

>The knock you are detecting at part throttle with the aftermarket chip is
>from lack of EGR... Guaranteed that the chip people only removed the EGR
>and didn't fix the EGR timing and fuel tables to make it run right without
>the EGR...

Yep.

 GM adds timing and leans the fuel during EGR so there is no loss
>of power from the EGR.

As to this one, I have a bridge in Brooklyn you can buy!!

Yes, they lean it so that CO and HC do not go up, on account of less total
air, and yes, they advance it so that they get back some of the response
and mileage screwed up by EGR (mixture diluents are a knock resister, so
they CAN get away with more advance when EGR is on), but NO WAY you do not
lose power at equal MAP levels with EGR on vs. off!!

 Take away the EGR, and now the timing is way too
>high, and the fuel is too lean because the part of the combustion air that
>was recirculated exhaust is now air and it needs fuel.

Yep.

>This is why a lot of chip makers charge a fortune hoping no one knows what
>the tables contain... it shows they have no clue as to what they are doing.

What?!?--people involved in the automotive aftermarket who would screw
their customers?? Where on earth did they learn such tricks--working for
auto manufacturers before they went into making aftermarket stuff??!??

Regards, Greg