mpgs took a dump

[AF_Hemi]

About 2 weeks ago my mpg's took a dump on me. It was right around the same time I got the new tune, but Sean said the tune wouldnt really affect the mpgs that much at all (and if sean said it, i trust him). I went from an average 13ish to right around 9.5.

Any ideas what could cause this huge 30% loss? Sean suggested maybe the o2 sensors are going bad? How do i test that without buying new ones? Any other suggestions?

 

[Off_Road_Teacher]

Did you calculate the before and after both by hand?

 

[03MopaRamman]

IMO they are either workin or not, however have heard on other Chrysler Models that replacing them makes a noticable difference!!//

If it makes you feel better my avg is 10.2 mpg combined!

 

[AParrette]

mine is around 8 right now

 

[AF_Hemi]

Before this gets off track, I dont care what your mileage is. Thats not the point of this thread. The point is Im gettin 30% less than what i did 2 weeks ago and something wrong... I wanna fix it so i can get back to where I was.

The tune will probably hurt mileage a smidge (sean says max of 1 mpg), but the new torque converter will make up for it.

Teach, I always calculate by hand. The OH isnt usually far off though... .2 at most.


As for the o2 sensors, I only have 2 (03 exhaust). One in the DS header, one in the PS header (one in the PS has a non-fouler).

 

[Shiloh 24]

AF really the only way to truly tell if an 02 sensor is bad is with a diagnostic scanner. We look at the normal voltage for the sensor and compare that to what it shows. If the voltage is too low or WAAAAY to freakin high the sensor is cooked and you'll need a new one. Without a scanner idk how to check em, you might pull em out and clean em up with some brake clean see if that helps?

 

[KGBIGCOUNTRY]

Hows the a/f look? Im guessing your a/f will show constant rich if your thinking your just dumping fuel.

 

[cheapbeater]

i assume you did a computer reset? checked your air pressures, ran some fuel injector cleaner, went to a different gas station, kept the pedal off the floor...? just thinking out loud..

 

[AWE Daniel]

It was right around the same time I got the new tune

Maybe you could put the old tune back on just to rule out the new tune? Not saying there is anything wrong with the new one, but I would just make sure. The timing is too close there.

 

[truckin151]

Did the temps outside change a bit in the last few weeks? Does your state change to a winter blend as well?

 

[glass3222]

Have you been driving different? Datalogging wot runs? That could be the difference.

 

[Off_Road_Teacher]

Maybe a lot of letting the truck sits while it idles?

 

[Redtruck-VA]

Before this gets off track, I dont care what your mileage is. Thats not the point of this thread. The point is Im gettin 30% less than what i did 2 weeks ago and something wrong... I wanna fix it so i can get back to where I was.

The tune will probably hurt mileage a smidge (sean says max of 1 mpg), but the new torque converter will make up for it.

Teach, I always calculate by hand. The OH isnt usually far off though... .2 at most.


As for the o2 sensors, I only have 2 (03 exhaust). One in the DS header, one in the PS header (one in the PS has a non-fouler).

A higher stall torque converter does NOT improve mpg. The only time you will not be penalized by having a higher stall converter is when it is locked up at highway speeds. I did both gears and TC at the same time and it was pretty much a trade off with mixed driving. Straight highway it remained about the same, town driving a slight loss. What the gears gave me the TC took away. But these mods were done for performance not mileage. I'm figuring heads and cam will also hurt mileage. Anyway, I'd watch the A/F readings to see if you aren't running rich. I see O2 sensors as either being good or bad. I frequently clean my K&N filter and TB, I'm poor at changing plugs. And of course a little playing dumps the mileage. Mileage wise, I think you should expect 12-15 mpg for mixed driving.

 

[truckin151]

I did my tc about 2yrs after I did the gears, didn't see any increases or decreases in any mpg hwy/city so I doubt it has anything to do with the converter.

When you get back to running it normal, so no data logging and the tune is finalized, then I'd run a couple tanks and see how its going. Data logging and getting a tune figured out is not the best time do any sort of mpg tests.

OT - But are you charging bullet a gas fee to come down there for the cam install now LOL...

 

[AF_Hemi]

all good suggestions guys. i guess i'll just let it play out. No im not charging bullet a gas fee. Im actually losing quite a bit of money to go down there and do this for him, but its not biggy -- tryin to help a brutha out.

 

[Redtruck-VA]

all good suggestions guys. i guess i'll just let it play out. No im not charging bullet a gas fee. Im actually losing quite a bit of money to go down there and do this for him, but its not biggy -- tryin to help a brutha out.

Well done, maybe a side wager will balance the books........ I see this as great fun, maybe there will be an occassion when we can get a mess of trucks together and do some bragging and racing....

 

[Silverbullet08]

and i GREATLY appreciate it....

 

[truckin151]

all good suggestions guys. i guess i'll just let it play out. No im not charging bullet a gas fee. Im actually losing quite a bit of money to go down there and do this for him, but its not biggy -- tryin to help a brutha out.

I was just jokin man, its a mini vacation right. Should be fun. I'd say you should see if you could swing through AZ on your way back and we can head over to the track for a night but its probably to far out of the way.

 

[AF_Hemi]

i'd love to, but yeah too far out of the way.


just did 20 miles city, and 200 miles highway. Truck loaded with 6 people and a bed FULL of camping gear. Estimate roughly 7500 lbs total weight averaged 12.2 mpg. so not as good as it was, but acceptable considering the performance