Gas milage dropping-no codes

[daveleeander]

My '02 , 4.0L has had a drop in milage from 21 on the interstate down to 18/18.5. My driving habits have not changed. This has been within the last two months.
I just pulled codes through the ODBII plug and nothing came up.
Could an O2 sensor be going bad (or bad already) and the computer compensate for it without setting a code?
I have noticed it idling high for what seems to me to be a longer period of time recently, but it has also been colder recently.
I also ran a can of seafoam through it within the last 3 months.
What else could be the trouble. I have replaced the IAC valve within the last four months (rough movement in D and P when cold) cured, new plug wires, plugs only have 30K on them probably (dual electrode if that means anything), I have not pulled them to check for deposits.

Edit: I just read Glaciers thread on the MAF. I haven't had that out for a few k miles. Going to check and spray it.

Is there anything I can check before I carry it into the stealership??

Dave

 

[joefnh]

The colder temperatures. I have noticed the same thing in NH.

--Joe

 

['92Bauer]

Winter temps and warming up your car, could also be winter blend gas.

 

[carlover]

id say its due to the winter gasoline blends. Id clean the MAF and see if that helps, maybe some good fuel injector cleaner. But more than likely its just that time of year.

 

[Ranger379]

ya if its cold and your letting it warm up, then say bye bye gas mileage, last i checked i was getting 6.6mpg due to this damn sub zero weather lol what about pcv valve and air filter?

 

[daveleeander]

Cleaner is good

I cleaned and re-oiled the air cleaner a couple of weeks of ago when I changed oil (Amsoil).
I haven't thought about the PCV Valve
I'll check that.
As far as the cold goes, it certainly is
I guess I was thinking like I did when I was flying, colder the air, better the performance of that old Piper. Of course, that was due to density of air giving the prop something to bite into. I don't think the Exploder bites the same way

I'll replace the valve. It's probably past due at 128k.

Thanks,

Dave

 

[Ranger379]

ya i dont know how much if at all that may affect gas mileage, but its a 3 dollar part it cant hurt lol