my 88 xj is getting bad gas mileage...i assume, because ive heard 4.0's aren't good on gas to begin with. i have a suspision my 02 sensor was never replaced and i was wondering if i can find out if its bad or not before i drop 50 dollars on a new sensor? i know that there is an idiot light in the dash and that when its time to replace it, it goes off and to shut it off you have to replace the stupid light/relay/thing in the dash and i have a pretty good believe that the last person who owned it just cut it out or whatever and never replaced anything. any ideas? also, besides cleaning the TB and filling my tires, what else can i do to increase MPG?

Theres all kind of threads about MPG. Try looking something up.

What kind of mileage are you getting? Right now I'm stock and average around 16 to 17 with in town and some highway driving and on the last trip I took I averaged around 19.2.

Here is how you can "clean" the O2 sensor. Manually open the throttle while the engine is running, bring the RPMs to about 2500. Now pull the vacuum hose off of the power brake booster and keep the RPMs steady at 2500, do this for about 3 to 5 minutes. Then reconnect the vacuum hose and then slowly lower the RPMs to idle. This may help your mileage increase by a small amount, and it don't cost you a thing.

to increase MPG you can always regear as your O2 sensor issue there is a scanner that can check the sensors and tell you if there good or bad. very expensive though in the 15k range so not many shops have 1. mine is just getting that scanner now. but if your gas milage is below normal then i would suggest O2 sensor is the first place you check.

ill try that tomorrow when i get some time, but can you pull the sensor out and use some kind of cleaner like carb/tb cleaner?
i want to regear it badly, it only does 95 on the highway

i havent really been able to try to find out, but id guess im somewhere in the range of 10-15, if that. its definitely not good.

Never try to externally clean an oxygen sensor; you will ruin it.

Oxygen sensors have a finite lifespan of between 100k and 150k, depending
on engine efficiency.

They are too often overlooked. Replace it if there is any question! NTK or Bosch
are good sensors. Ebay= no way for engine management sensors, unless it is a confirmed name brand.

??? where you hear this

sorry dont mean to hijack the thread but it goes with it.... does anyone have pic of the o2 sensor installed still. do you get to it from the top or the bottom of the engine. im new trying to learn the ropes

more info on you vechicle will get better return.

oops sorry i gotta 1992 chereokee loredo 4dr

think you only got one exhaust pipe by drivers feet by motor around 8 inch down from exhaust manifold

We have had a lot of OBDII training and training for our new Snap-on scanner, the instructor showed us the trick to clean out the cat convertor and burn off any gunk that is on the O2. I didn't think it would do much, but I tried it and was able to see the difference on the live data stream on the scanner. The O2 moved faster and there were less hydrocarbons coming out of the exhaust.

some companies have the option of o2 sensors without the connectors. they are considerably cheaper. only do this if the original connector is in good condition though cause after you cut , splice and waterproof, you still need a good connection. also, i don't know if you want to buy a o2 sensor socket. i did but it didn't fit between the manifold and the inner fender. waste of money on my part but now i have one my buds can use.