Got a couple questions for you guys.

Have had a 4.7L 4x4 quad cab for about a year.

Was experiencing 17-19 MPG on highway, and 14-16 MPG in town.

about six months ago, this dropped by about 3-4 MPG no matter what I did. No changes had been done to the pickup. Same PSI in tires. I had a check engine light come on intermittently, but it hasn't been on in a few months.

The pickup has 80K miles on it. Not sure when the last tune up was, so was going to change plugs first and see what happens. It has a K&N on it already.

Would you recommend changing the 02, or does it only need changing when the light comes on?

Any other ideas to check for the sudden loss of MPG?

 

There are four 02's on the 4.7. At 80k I would think they are due
for replacement.

The check engine light being off doesn't always mean there is nothing
wrong.. I'd still do the 3 key on and off thing and see if any codes
are displayed.

Some auto parts stores will also scan your system for free.

If you're not sure when the plugs were replaced, I'd go
ahead to replace them.. I don't have my owners manual in front
of me but I *think* I remember seeing they recommend plugs
being replaced every 30k... You be the judge of that..

You might try resetting the entire computer system before you
do anything and see what happends... Can't hurt...

 

I had the same thing happen in November. Mine's a 99 3.9 4x4, and it dropped from an average of 16-17 to 13.5 every tank. I live in Michigan, so I believe it's just the winter months. Everyone I talk to about it says the same thing, it's because of winter. I'm expecting to see it go back up in the warmer months. I changed the plugs and rotor after the drop and it has made no difference.

 

Thanks!

how do you reset the computer??

 

To reset computer... Remove the NEG terminal from your battery.
Take your key and put in to START and hold there for 10 to 15 seconds.
Put key to off. Reconnect your battery. Finished.

All fault codes are cleared. If you have a problem after the reset, the
fault code or codes will return..

 

cool thanks!

I changed the plugs, they looked marginal.... But what is wrong with the engineers at Dodge? Changing plugs shouldn't be so much of a pain in the butt. I've worked on cars my whole life, and the only one harder to change plugs was an old corvette with cheap headers. We had to take the fender off!

I tried the scan 3 starts thing, and it didn't give me any codes. Does it normally show them where the odometer is?

 

Alright... Put a few tanks on the pickup, and not really much better.

16.7 on the highway going 55.

I am getting no codes, or check engine light.

Think I should change the front 02 sensor?

 

Why would you only change the rears?? [sm=confused06.gif] ... don't those just tell the computer if the Cat. is working properly? [sm=confused06.gif]

how much do the 02's run any way ?$$?

[sm=icon_cheers.gif]

 

75 bucks each when I checked.

150 would buy a lot of gas if they don't need to be changed!

 

you said the magic word!!!!!
~~~Pee Wee Herman~~~