BlvdKreeper

Well heres the deal..last december I bought a 97 xj auto bone stock with 156K on the clock.It had a check engine light.I took it to my mechanic so he could run a computer scan and both the oxygan sensors came up bad.BUT he also told me the engine was running rich on gas(came out on the scaner)..well I replaced both oxygen sensors and the check engine went away.

I did a full tune up the following week(rotor,wires,etc,)but it made no difference at all.with gas at $4.48 its starting to get to me.my brother has a 97xj as well with 150k and my ride is no match to his when it comes to gas lolz


what are some things I can check,replace or do solve this problem? i really dont feel like going back to my mechanic so he can check it if its something I can do myself.

BlvdKreeper

It Also has a new hi flow cat and super 44 flowmaster installed last month.

notop46

Change the air filter, tire inflation, and unload any un-needed weight. Take it to Autozone, or other chain auto parts and have them run the scan for frre to see if it has any stored codes (hope your mechanic cleared the old ones).

You did not provide much data, so more would be helpfull. My 1990, 5sp, 4 liter, 4WD with 235/75/15 Michelin LT tires and 234k miles gets ~16 city and ~19 highway.

BlvdKreeper

I'm running 235's as well. I got nothing in the back besides my tool box and spare

notop46

What has your mileage been running? I have spare, toolbox, and 100 lbs of recovery gear in back. My rack is EMT (pretty light), and the bumpers are heavier than stock but not too bad (~40 lbs each).

Check the spark plugs to see if they are a light tan color (good mixture), black and sooty (rich), or white (lean)

1armyguy

What is your idle running at and does it fluctuate a lot while sitting still? I would do the above mentioned by changing the air filter and also cleaning the throttle body and either replace or change all the sensors that are attached to the throttle body as well. With a mix of city and highway driving, 235/70/16 tires and about 80 - 100lbs of weight in the back, I still average 15.5 -16.5mpg's. This also includes front and rear hitches and a pair of sturdy rock sliders and a 3" Series II Rough Country Lift.

Good Luck

no rdplz

Simple solution - reset your ECU. It will allow your computer to "relearn" the fuel/air trim levels over the next 50 key cycles. Drive like a grandma during these cycles and you should be good to go. If it's still running rich after 50 cycles, then take it to a parts store and have them check for any codes.

8sec-z

Check your fuel pressure regulator via the fuel rail port. Maybe the reg took a dump.
Also, maybe one of your fuel injectors has a damaged tip and is flooding its cylinder. Check each spark plug for the correct color and make sure they are all the same color. If one is greasy flaky black, well then you have a problem with that cylinder..G/L

BlvdKreeper

I checked my spark plugs. They all have the normal wear. No oil leaks, no uneven wear.

BlvdKreeper

How do I reset me ecu by the way?

White92

Disconnect the negative terminal on the battery.. let it sit for 20 minutes. That will reset the ECU

BlvdKreeper

Alright. I'll try it when I get off work

kyledye25

I have a 96 bone stock XJ. Just did tune up. Plugs, wires, cap and rotor. Also did an "efi". I work at a Toyota shop. Its like running seafoam through the vacuum line but it was a BG product. Worked out really good. I just filled up and my gas mileage was 18mpgs. thats a little highyway and mostly city. When I got it the gas mileage was 15 or so. Its only been 3 tanks of gas. Since all that was done. I would reset your computer like stated above and drive very gingerly. See what the nect few tanks get ya. if its still bad you still have a problem.

tjwalker

Get data so you know where you are at. For both now and in the future.

Get 3 gas mileage samples. Must be calculated. Miles driven divided by gallons consumed.

Anything less is guesswork.

Post what you find.....

BlvdKreeper

I cleaned the throttle body today. I'll see how it runs within the next few days. Can any of you recommend a good fuel injector cleaner? I also have a set of extra fuel injectors that I might want to replace with in the future. The ones on the jeep have a whole bunch of surface rust.