joedarr33

So i have a 89 cherokee 4.0 4wd. 4 door. Its lifted 4.5 inches with 32's.
I just did a new air filter and plugs not to long ago.

I calculated here this month and i have only got about 9mpgs...

I have a new fuel filter I'm going to put in it.

Idk what else i could mess with.
i have 3.55 gears, maybe i desperately need to put new gears in?

PDEM87

Have you looked close at your map sensor vacuum line? If it's plugged or leaking, mpg will suffer! Have you checked your tps voltage setting? How old are your injectors? Are you familiar with Cruiser's mostly Renix fixes?

McCaffrey

Did you change the speedo gear when you put larger tires on? Unless you change it you're driving further than you think you are for your calculated mileage.

PDEM87

McCaffrey, good point on the speedo. I did some math and the miles traveled may be up to 20% more than what his speedometer is telling him. So instead of 9 mpg , it's probably more like 11 mpg.

cruiser54

Good thing to know for the OP.

Also, a fuel filter that's dirty won't reduce MPGs.

Which plugs were used? No cap, rotor or wireset?

Since it's an 89, it needs the procedures outlined in posts 1,3,4 and 5 in my Renix Tips signature done.

McCaffrey

Mine's an 89 too and gets much better millage than the OP. I've only done Cruiser's #11 so far but once I move I want to do more items.

DFlintstone

Does the idle cycle every 20-30 seconds so? Fine for a bit, then slows, almost dies, catches up revs a few seconds, then repeat? Mine did that with a dead 02 sensor.