P0442 and bad gas mileage

[Noshirtganshirt]

About 8 months ago, I was getting CEL with a P0446 (common problem) so I replaced the charcoal canister with another used one. Fixed my issue.

Fast forward to now. No CEL, but my Ultragauge picked up a pending code for P0442.

Thought it was just winter gas but I can almost see my gas gauge moving to empty. Was getting 280 miles on a tank (Supercharged). Now I’m lucky to get 220.

The pending code hasn’t come back on yet. It’s been almost 2 weeks now.

I know the EVAP codes are the worst things to chase down but the drop in gas mileage is puzzling me.

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[sdwaltz]

About 8 months ago, I was getting CEL with a P0446 (common problem) so I replaced the charcoal canister with another used one. Fixed my issue.

Fast forward to now. No CEL, but my Ultragauge picked up a pending code for P0442.

Thought it was just winter gas but I can almost see my gas gauge moving to empty. Was getting 280 miles on a tank (Supercharged). Now I’m lucky to get 220.

The pending code hasn’t come back on yet. It’s been almost 2 weeks now.

I know the EVAP codes are the worst things to chase down but the drop in gas mileage is puzzling me.

Sent from my iPhone using Tapatalk

Nothing to offer, but I'm blown away that you were getting 280mi/tank and feel like 220 is bad.

I've been lucky to get 190-200 for the past couple weeks, down from 220-230...sounds like I have a problem.

 

[Noshirtganshirt]

Nothing to offer, but I'm blown away that you were getting 280mi/tank and feel like 220 is bad.

I've been lucky to get 190-200 for the past couple weeks, down from 220-230...sounds like I have a problem.

Yeah I’d say you have something going on haha.

I know these things aren’t eco vehicles, but we wouldn’t even be talking about this if it was such a drastic change in mileage along with an Evap code.

 

[SIKHILUXSURF]

ive been on the same boat for the last year. it is mind boggling. i used to do about 250-280 per 3/4 tank supercharged as well. after the knock sensors went bad. ive never been able to recover that mileage. now im lucky to get 180-190 per full tank no codes since the knock sensors were replaced.

 

[Noshirtganshirt]

ive been on the same boat for the last year. it is mind boggling. i used to do about 250-280 per 3/4 tank supercharged as well. after the knock sensors went bad. ive never been able to recover that mileage. now im lucky to get 180-190 per full tank no codes since the knock sensors were replaced.

Funny you say that. I replaced my knock sensors a couple months ago as I was getting a CEL and limp mode.

I hunted down a P0446 Evap code about a year ago. Worst thing ever to try and diagnose. Ended up being a bad charcoal canister.

Now I’m getting the P0442

 

[jlandrey]

Funny you say that. I replaced my knock sensors a couple months ago as I was getting a CEL and limp mode.

I hunted down a P0446 Evap code about a year ago. Worst thing ever to try and diagnose. Ended up being a bad charcoal canister.

Now I’m getting the P0442

I am having the same issues - started with knock sensor and then EVAP
I will replace the charcoal canister, have you diagnosed the P0442 yet?

 

[spartacus]

P0442 is a precursor code for p0440. I fixed this on my truck few years back. After a start the vacuum is sealed in the system and the ecm monitors the pressure and if there is a huge leap in pressure it throws 0440 but it also monitors the small leak which is p0442.
Check all vacuum hoses for damage, cracks,loose disconnected etc
Check fuel cap o ring in good shape and the cap is snug
I did a propane test on my vacuum lines and found the culprit.
Other things to look for fuel tank overfill check valve. Open or short in vapor pressure sensor circuit. And of course leak or crack in fuel tank or canister or even the ecm.
Good luck.