I have an 89 Cherokee Laredo that gets 8 MPG in the city. So far I have replaced the plugs, o2 sensor, fuel filter, air filter and vacuum harness. I checked my tire pressure and it is fine. It idles around 1000 RPMs and bounces around a tiny bit. Seems to be a lot more effiecient on the highway. I am starting to think it is just an old Jeep and this is the best it can do. Any ideas?

 

How are you calculating miles per gallon?

 

This is NOT normal.

Cap, rotor and wires are due to be changed with the plugs.

Intake manifold bolts loose?

Line to the MAP sensor or fuel pressure regulator leaking?

Go to www.cruiser54.com and do Tips 1,3,4, and 5 soon.

 

My 90 w/ 4.0, auto, 4.10 gears and 33s gets 13.2 mpg currently. Mine is running rich, you can smell it at idle. I can only IMAGINE what your's smells like, must burn your eyes! Definitely not normal.

 

I calculate my miles by setting my odometer to zero when I fill up and dividing that by the gallons it takes to fill up next time.

I will do those tips as soon as I get back from a trip I am leaving on tomorrow. By lines to the MAP sensor are you talking about electrical wiring to the sensor.

I am taking it to the coast tomorrow so I will calculate the MPG on the highway

 

vacuum line from the throttle body to MAP and vacuum line to fuel pressure regulator. If they're not perfect bad fuel mileage will be a result.

 

Vacuum lines are in good condition. Could it be the MAP sensor itself causing such a problem? The weird thing is it gets 15 MPG on the highway and only 8 in the city.

 

Wow!

We have 7 posts on a "sub-10MPG" thread and so far nobody is trying to tell him to drive more carefully or it's his big tires!

Nice!

 

What condition is your exhaust in? Leaking? Throwing off the O2 sensor readings?

 

When I got the car I was told it had a very minor manifold leak. I took it to my mechanic and we decided it would be smarter to just leave it be.

 

Have you checked it?

 

My mechanic looked at it and said it was small enough that it was not worth fixing.

 

Check them yourself.

 

Probably stretched timing chain/bad guides, timing is off due to this.

My Cherokee got 21.8 mpg at 65 mpg with all terrains, 1,000 pounds of people and 200 pounds of stuff in the trunk. This was after having the timing chain replaced and the distributor.

 

Are you one o those axe/chain saw/machete murderers we hear about?