99 4.0l decreased milleage

[99ABTJ]

Recently my '99 TJ 4.0l is not getting the milleage it had in the past. Very sudden drop. I've recently done a tune up - plugs,wires,dist. cap, air filter. No change evident. I've added some injector cleaner and next when my tank gets low enough I'll add some fuel system conditioner. Other than that, anybody have other ideas. Fuel filter? If so, is it hard to change?

 

[SteelHeadz]

Any performance issues like lack of power?. The fuel filter is located on top of the fuel pump module. Lowering the fuel tank is required to replace this filter. I would suggest you do it at the minimal fuel level to make it easier.

 

[99ABTJ]

No performance issues that I can notice, thanks for the filter info

 

[mud4feet]

When my O2 sensors went bad on my 4banger, I noticed a SIGNIFICANT drop in fuel mileage. But I also noticed a gradual drop in performance. When they get bad enough, they'll trigger the CEL. How old are your O2 sensors?

 

[99ABTJ]

The jeep is '99 with 135000 km's, I've had it since 100000k's - I assume that they are original. Are these sensors something I can check/replace? What's a CEL?

 

[carnuck]

Sounds like you got your first batch of "oxygenated" fuel. Economy drops about 20% with the added alcohol in many vehicles

 

[Saddle Tramp]

The jeep is '99 with 135000 km's, I've had it since 100000k's - I assume that they are original. Are these sensors something I can check/replace? What's a CEL?

Oxygen sensors screw into the exhaust system, usually a bung welded into the pipe, and look kind of like a spark plug; easy to replace.