2000_silver_xj

Fairly new to owning an XJ, and it seems to be getting a lot worse gas mileage than I thought it would. I'm averaging around 13.5, have a 4 inch lift an 31's, and the only performance upgrade I have made is cat back Banks exhaust. Does that seem right to everyone? I ran a injector cleaner through the intake, through the gas, and will be replacing the coil pack and spark plugs. Anything else I should look at? Or does that seem normal with the lift and tire size?

KJamesJR

Think this is in the wrong thread.

You driving in the city? Seems like it could be pretty normal for your set-up but I'm not familiar with lifted XJ's. I'd do a full tune up and run the tank down again and report back. I like to try and fill up on an 1/8th tank at the same station using the same pump if possible.

2000_silver_xj

Ok thanks for the feedback! I already have the stuff ordered for the tune up so I will will post back with results after i get it back from the fab shop. Getting rock sliders, frame stiffeners, front and rear shackles, and corner cut plates welded up

KJamesJR

If you're using a roof rack, those have been rumored to put a good dent in your MPG as well. Just an FYI.

EZEARL

Checked your O2 sensors lately?

2000_silver_xj

Just changes both O2 sensors. I am going to change the spark plugs and coil pack and see if that improves things. It has 164K on it and the previous owner did the bare minimum if even that

Ralph77

I don't think I would mess with the coil pack right away.
For starters they are not cheap. Even aftermarket ones.
Kind of thinking that this is one of those things that you might want to buy a Mopar one of.
Which probably means it is going to cost that much more.
I would give the springs and boots on the coil pack a quick look.
Just those can be bought at any auto parts store.

2000_silver_xj

I picked up a coil pack from Quadratech, wasn't too horribly priced. I tend to go overboard, but if I am pulling something like a coil pack to change spark plugs on a 20 YO vehicle I am going to replace the coil pack. That's more of a personal preference, and like I said, probably overkill. Once I do the tune up and install the THOR cowl kit I will report back on what impact to my MPG there is. Outside of everything mentioned in this thread already I am not sure of anything else that would impact the gas mileage that wouldn't be completely obvious (i.e. gross exhaust leak or misfire of some sort)

lawsoncl

Beside checking the O2 sensor and it's wiring is not damaged or melted against the exhaust, also check the coolant temp sensor. If it's bad and telling the computer the engine is cold, that will kill your mileage too. Same for checking the TPS sensor, as the computer thinking you're wide open throttle will kill mileage and also cause shifting issues.

2000_silver_xj

I will look into both of those, hadn't thought of either of them and how they would impact it. Thanks!

PatHenry

Being you're sinking some money into the Jeep, it might be a good idea to consider one of the ODB2 connected monitoring tools. I've heard "Torque" as an app name that's thrown around quite a bit. Then you can monitor your fuel trims, engine temp, O2 signals and all that stuff in real time and get a very clear idea of what's going on with your engine.