Well my gas mileage has deminished on the XJ ( i know they dont get good mileage to begin with) and i have so far had the basics done within the year, air filter, plugs,oil,dif fluids, drive shaft and axle replacement lask week, o2’s seem to be running good(scanned), exhaust isn’t plugged that i know of. So all i can think of is fuel related matbe, how do you tell if you have a leaky injector or fuel prob?
I am getting about 10-12 if i am lucky a gallon, should be around 14-16 even with the lift adn 31’s.
Would a vac line cause bad mileage or should i stick with looking into injectors and fuel issues?
whats up Devon, My truck gets worse gas mileage in the winter because I let it worm up longer in the morning and after work. But, your jump in mileage is pretty big
bad vac line could cause it but you should set a check engine light first. unmetered air entering is going to be compensated by the pcm adding fuel, when the fuel trim stategy reaches it’s limit it’s going to set a lean code.
if you can scan check your long term fuel trim at idle, if it’s high positive it’s possible you have a leak
have you changed out the PCV? atleast spray it out with some carb cleaner
bad vac line will not set off a code on the 4.0’s, these motors are more forgiving than anything i have ever worked on before SES wise. Havenet scanned for LTFT yet but i have see bit and didnt look out of the norm…
4.0’s are not this bad even with lift and 31’s i have:bash:
you still have the same number Joe? As far as the mani i have heard about that being a big prob but i do not hear or see a crack and the head? Restore? A buddy of mine is going to do a complete BG kit in it this week but i doubt it will help
I’ll give you a ring tomoorw then, but that restore stuff seems the same as all the other advertised BS that says it will increase this and add that and put your motor back to OEM and like it had only 2k on it, right?
How’s the exhaust mani? They crack and you get a shitty O2 signal.
My 01 gets 17-20 with stock sized tires, but it’s a 5spd with 3.07s, not sure which gearing you’re running. I had an injector fail, but it didn’t leak, it just quit firing. It started and idled pretty well, didn’t really notice until I hit the gas, and I could really notice the miss. I swapped it out with one from advance and it’s been flawless since then.
In the winter, I see 15 or 16. I dunno, check over the exhaust manifold, that’s a big source of trouble on these. The cracked head doesn’t seem to hurt gas mileage at all. You just lose coolant slowly without a trace, then eventually the bitch overheats like a mother and you know you’re screwed.
I tried to check the mani but don’t think i found any cracks, i cannot hear a leak at all and i have the shitty california emissions bs where i have four 02’s and tw osmall cats on the mani itself as well. As far as power lose it does not feel like it at all nor does it have a miss, at idle it a tad jumpy and rough though.