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160 miles on a tank of gas??

xj_convert

NAXJA Forum User
Location
Berks Co, PA
My 91 XJ has 70K on the motor, and runs great, other than a pretty good shudder when it first lights on starting. Idles well, plenty of power.

This is the first fuel injected vehicle I've owned, so other than the typical tune up stuff, what are some leading causes of bad MPG?

The motor was replaced at 130K- for all I know the O2 sensor, etc was re-used
on the new motor. I *did* read somewhere that there is an air sensor before the throttle body which can benefit from being cleaned.

My 87 Grand Wag with 150K mile 360 gets better MPG than the XJ, and that's just wrong!

Thanks

xj_convert
 
Fuel pressure reg. Take the vacuum hose off the reg. and see if there is raw fuel in it. Try priming the system by turning the key on and see if the reg. leaks w/ pressure on it. Sometimes it takes a combination of both the pressure and vacuum. If the vacuum harness is soft and squishy it probably leaking. The O2 could also be to fault, but check the reg. first.
 
Replace the o2 sensor. It doubled the mpg on my son's 89 and I'm getting 22+ highway on my 96. that's slightly more then 300 per tank. Also make sure it's getting to operating temperature, 210 degrees, asap.

JoBo
 
Thanks for the suggestions.

The motor is getting to temp, all otherwise feels and runs good... even the wires look newish. Because I don't know the entire maint history, it's getting a full tune up to get to a baseline, but given the (good) way it runs, I figured there was some kind of FI/ECU condition happening to make it chew through gas like it is.

I've done a lot of HEI ignitioin design, and am going to convert the ignition to HEI, put an air intake on it, plugs, wires, and check into the issues you guys mentioned.

Where is the gas filter on the XJ? Near the tank, or in the motor bay?

xj_convert
 
Also do the cleaning thing, you may have an injector stuck open, can of chevron Techron to full tank of gas [big bottle of techron, not the small one].
 
xj_convert said:
Where is the gas filter on the XJ? Near the tank, or in the motor bay?

xj_convert
Near the tank. It's easy to find....just look underneath in the area near the gas filler tube.
 
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