Air Pump, O2, Bad gas mileage

[Austin T5]

My gas mileage is terrible. I followed the MAF connecetor/MAF cleaning instructions in previous posts. It seemed like it worked temporarily 9one trip), however, gas mileage is back down

Will a bad air pump degrade mpg? How can I determine whether or not my air pump is operating correctly on my 97 T5? I can hear the air pump on my 97 GLT..nothing on the T5.

Might it be O2 sensor?

I do not have any CEL light on, nor are any codes stored. I'd like to start at the likely source, I just have no idea which one is the cuplrit due to lack of codes, CEL.


Thanks for any suggestions.

[White850Turbo]

I believe a non-functional air pump will usually throw a code. How many miles are on the car and has the o2 sensor been changed before? One big culprit of bad gas mileage is torn or leaky vacuum hoses. Check all of the little hoses that run from the Boost Control Solenoid to the boost pressure regulator, fresh air intake hose, as well as the one that goes on the underside of the turbo. Also, there is a little rubber elbow that is rather difficult to see and to access that can be found on the passenger's side of the intake manifold directly diagonal from the power steering reservoir. It is infamous for developing leaks. There is also a hose that runs from the EVAP valve to the driver's side of the intake manifold. There is also a hose that runs from the compressor bypass valve up to the driver's side of the intake manifold. All of those are the biggest causes of poor gas mileage. I had a torn vacuum line that when replaced, made a HUGE difference in gas mileage.

[Austin T5]

The T5 has only 36000 miles on it. I have checked most of the hoses and the main elbow on the manifld is good to go.