I did a complete tune up changed all the filters with no change in power. It gets 175 to a tank of gas. The only code is for the charcoal canister. I had another s70 just like this one and it had three times the power. Any idea what it could be?

 

Shot in the dark, but is there a chance the brakes could be dragging....i.e. stuck caliper. In addition to all filters (I'm assuming you changed air, fuel and oil) did you change the plugs, plug wires, distributor cap, rotor, clean the throttle body.as well? There are a lot of things that can cause low power, high fuel consumption. Charcoal cannister could mean fuel is getting dumped into it instead of just vapors.

 

Yes I changed all of the filters, plugs, cap, rotor, wires. Brakes not dragging. But didn't clean throttle body. Do you think I should clean the maf sensor too?

 

if you clean the MAF, use a product like CRC MAF cleaner, not generic carb cleaner to avoid messing up the wire grid. Have you used a OBD2 reader to measure fuel trim? A wonky front O2 sensor can cause poor mileage as can air leaks. Given you have a cannister fault code, I'd inspect the J tube vacuum line back near the cannister (should be some vids on Youtube to help)

 

Could be low compression, One cause of that might be the timing belt not timed correctly,

 

Usually a bad MAF sensor will throw a code, but it wouldn't hurt to clean it. You could unplug it completely and see how the car runs, but it will most likely throw a code that will need to be cleared.

 

If you are really getting 10 mpg with no codes, then there is a lot of gasoline going somewhere. I don't think an O2 sensor could be that far off. In fact, I don't think any combination of sensor errors could do that without throwing codes. The way the cars are built, late spark timing is impossible.

What engine temperature does the car think it has? If the car always thinks it's 40 below zero all the time, that could have some effect, and the car would never realize it was wrong.

What is the exact code for the canister that you do have?

 

^^ ck it.