Fuel Mileage Has Dropped Off

[turner-2000tj]

all of a sudden my MJ is getting 9mpg on a good day! :doh:  Its a 91 with a complete 98 conversion.  I do not have the emmisions system all hooked up.  Would that cause bad mileage?  What should I look at first to see why its getting bad fuel mileage?

 

Thanks is advance!

[92tanMJ]

If it were me, I would hook up the emmisions system up first and then reset the PCM and see where that gets ya. I'm pretty sure the newer systems need all of the emmisions stuff.

 

And then theres the normal 'how old are you plugs/cap/wires' questions? Also did you lift it or put on new tires or anything like that?

[Biotex]

So what were you getting before, and what have you changed if anything?

 

Were you getting better mileage before without emissions hooked up?

[92tanMJ]

So what were you getting before, and what have you changed if anything?

 

Were you getting better mileage before without emissions hooked up?

 

I'd assume he never hooked it up after the swap.

[Biotex]

 

So what were you getting before, and what have you changed if anything?

 

Were you getting better mileage before without emissions hooked up?

 

I'd assume he never hooked it up after the swap.

 

That's what I first thought, but he uses the phrase "all of a sudden" so this leads me to believe he was driving it, and getting better mileage, then all of a sudden???

There has to be more to the story if you know what I mean. Impossible to help diagnose whith all the missing facts...

[92tanMJ]

 

 

So what were you getting before, and what have you changed if anything?

 

Were you getting better mileage before without emissions hooked up?

 

I'd assume he never hooked it up after the swap.

 

That's what I first thought, but he uses the phrase "all of a sudden" so this leads me to believe he was driving it, and getting better mileage, then all of a sudden???

There has to be more to the story if you know what I mean. Impossible to help diagnose whith all the missing facts...

Oh I know, thats what I thought but I was just saying. lol There is a lot of missing information on this one..