I have a 2000 accord 5MT with the F23A4. lately my gas mileage has been dropping and has gotten down to an average of 25 mpg. I always got 32 on the highway and 27 or so around town, now I get about 26 or 27 on the highway and about 24 around town! I have a code p1457 (EVAP) and I diagnosed it was the bypass solenoid because it's like a dead short when you try to power it and all the others work properly, but I've always had this code and it hasn't gotten that bad of gas mileage before. I've replaced the o2 sensor, plugs, dist. cap, rotor button, and converter. not sure if the evap code can cause this or not. any help is appreciated. oh and I know the weather is getting colder but it didn't affect it like this last winter.

 

Check for any exhaust or fuel leaks. Has the car gotten any noisier? That could be an exhaust leak and that can lead to a loss of power and worse gas mileage.

 

No, there are no fuel leaks, and the exhaust only has a very tiny leak (not even noticable)

 

Is the exhaust leak anywhere near the front O2 sensor? The sensor actually measures oxygen DIFFERENCE inside vs. outside. So exhaust blowing over the outside of the sensor will throw off the measurement. Same deal for crud on the outside of the sensor.

 

nope, it's behind the converter, and the front o2 is the one I just replaced so it's perfectly clean. I also notice it doesn't have the power it did when I first got it, and I only put about 15k on it since I got it. when I first got it I had to see what it would do lol, and it hit 215kmh without a lot of trouble, but now i can barely hit 200 down a big hill!

 

if the CEL comes on, first thing I do is wipe down the sealing surfaces on the gas cap and
fill spout with a clean or damp rag. On various cars this clears CEL in <2 days.

But, but, I've no recall this impacts gas mileage.
Have seen a noticeable effect of temp on gas mileage though.

$.02 - don't know if this is your case.

 

thanks for the reply but my code is p1457 which is the canister side of the tank, if it was something like the gas cap it would be a p1456. I'm gonna pick up a pcv valve tomorrow, they are only like $2, I seriously doubt it'll help but it's worth a try i suppose, might help with the small oil consumption.

 

I just cleaned my EGR valve, so I'm gonna see if that makes any difference.

 

The canister vent-shut solenoid is a common failure that causes P1457. But there's still several other things that it MIGHT be. Including cracked & leaking vacuum hoses back around the canister. You could check them for obvious problems.

EGR valve and PCV valve will not cause P1457. But having those cleaned up isn't a bad thing.

 

yeah I know the EGR valve can't cause that code but I just wanted to see if it would help the fuel mileage and power issue any, an I already have checked all the evap hoses, they are in good shape.