I keep popping code p1416 on my 97 SS.

It seems to be something related to secondary air injection. I know nothing of this. I checked shbox's site, and will check the valve on the passenger exhaust pipe tomorrow.

Can this decrease mileage? Cause I am getting 16 - 17 on a stock engine LT1 without too much mashing the gas. A4 3.73 with shift kit and 3000 stall.

 

Its lack of air flow to the passenger bank of the exhaust, when the PCM cycles the AIR pump. It doesn't see the excess air appear in the O2 sensor reading. Check the rubber hose that is right next to the AIR check valve on the passenger side. If the check valve is leaking, it can melt the rubber hose. That will allow air to enter the exhaust, that air causes a false lean condition, the PCM adds fuel on the passenger side that the engine doesn't need, and fuel mileage drops.

16-17 in heavy stop and go traffic doesn't sound all that bad. 16-17 on the freeway would be not so good. Depends what kind of driving you are doing.

Just one possible scenario.

 

On mostly highway driving I get 17.5 mpg.

Even mix of city and highway I got 16.6 mpg.

I'll check what you said tomorrow, thanks.

 

Well I pulled the valve, still flowed air, but was stuck open.

Swapped in a new one.

I also checked and tightenned the header bolts. Some were kinda loose.