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-   -   Really really low gas mileage (http://www.wranglerforum.com/f290/really-really-low-gas-mileage-144309.html)

deepak 03-05-2012 02:47 PM

Really really low gas mileage
 
So i originally had 35 inch tires and my jeep gave 8 mpg. So then i decided to put stock wheels and tires. The jeep didn't do any better. It just improved by 2mpg. After that i put in new bosch platinum 2 spark plugs, new wires, new rotor and rotor cap.. The mileage is still around 10mpg with everything stock.. Any suggestion on what should i do next to improve it little bit.. I suspected it's fuel injectors so i put lucas fuel injector cleaner and still no luck.. Any other suggestion/ideas on what i should do to imporove it.

dmcg 03-05-2012 03:34 PM

Does it have a lift? Is it a 2.5 or 4.0? What year is it? You need to include these things. 2.5s with a lift get worse gas mileage then the 4.0s. Also, Jeeps like champion plugs the best. Replace your air filter with an AC delco. Don't use K&N. A failing catalytic converter will also give you crappy gas mileage and loss of power.
Jeeps get crappy gas mileage regardless. I'm lucky to get 15mpg in the city

banks316 03-05-2012 03:42 PM

O2 sensor

deepak 03-05-2012 04:13 PM

its's a 4.0l v6 with like 2 inch lift kit only...so i was thinking about going with k and n intake (the roundy roundy filter) but im not anymore. so how about fujita and any other brand recommendation.. it just passed smog like 2 monts ago so im assuming that it's not catylic converter.. i'll replace the oxygen sensor.. and should i get the valve tuneup done? and any other recommendations

deepak 03-05-2012 04:13 PM

and the year is 1992

DirtyRob 03-05-2012 09:12 PM

Quote:

Originally Posted by dmcg (Post 2105947)
Does it have a lift? Is it a 2.5 or 4.0? What year is it? You need to include these things. 2.5s with a lift get worse gas mileage then the 4.0s. Also, Jeeps like champion plugs the best. Replace your air filter with an AC delco. Don't use K&N. A failing catalytic converter will also give you crappy gas mileage and loss of power.
Jeeps get crappy gas mileage regardless. I'm lucky to get 15mpg in the city

You took the words out of my mouth. I don't know why but it is true about Champion plugs. The other suggestions are very good too.
Does your exhaust smell like fuel? If so you are runnig way rich
Does your floor get real hot behind the passenger seat? If so your cat converter is going bad. Just two things that come to mind to narrow it down.

deepak 03-05-2012 11:16 PM

so what is should do at this point is leave the bosch plugs, get new oxygen sensor, and new catytic converter... any air intake suggestions and how to fix the enrich fuel mixtured.. should i reset the computer to see what happens..

GrayYJ 03-05-2012 11:36 PM

If you change your converter, you are also going to want to change plugs.

Frenz 03-05-2012 11:36 PM

Hellz yeah reset the ecu.

banks316 03-06-2012 03:30 AM

Quote:

Originally Posted by deepak (Post 2106082)
its's a 4.0l v6 with like 2 inch lift kit only...so i was thinking about going with k and n intake (the roundy roundy filter) but im not anymore. so how about fujita and any other brand recommendation.. it just passed smog like 2 monts ago so im assuming that it's not catylic converter.. i'll replace the oxygen sensor.. and should i get the valve tuneup done? and any other recommendations

There's your problem you don't know what you. 4.0l are online 6 not a V

DirtyRob 03-06-2012 06:35 AM

Another option is take it to a mechanic that you trust, and let them look at it. You can throw parts at it and spend more money than repairing what it actually wrong with it, unless you just feel it needs a lot of stuff anyway. Good luck

Xpress 03-06-2012 01:27 PM

You have a 4.0 I6, not a V6. A V6 engine indicates that you have 6 pistons in a V shape, 3 pistons on one side, 3 pistons on the other. An I6 engine has all 6 pistons in a straight line. Basically I6 stands for Inline 6. Jeep never included a V6 engine in the Wrangler until the newer 2007+ JK models.

You need to do a FULL tuneup. That includes replacing EVERYTHING that is replaceable as a part of maintenance. I'm not entirely familiar with the 4.0, but here is a basic list of parts for you to go through and replace:

-Air filter (stock ones work just fine)
-Fuel filter (people always skip this one)
-Distributor cap
-Distributor rotor
-Plus
-Plug wires (all 7 of them, even the one coming from the coil to the dizzy)
-Remove the throttle body and scrub it out by hand with cleaners and a toothbrush
-Oil change (don't forget the filter)
-Replace PCV valves (if it has one, not entirely sure)
-Replace ALL vacuum tubing- it seems like a PIA but even a small leak can cause your engine to run odd
-Replace O2 sensor (get an OEM, Bosch O2's often fail prematurely)
-Replace MAF
-Flush out old coolant, replace with new GREEN coolant

And once all of the above has been done, run a good quality fuel injector cleaner inside of your gas tank- you need to have a full tank for the full bottle otherwise it won't work as intended.

Double check for exhaust leaks as well, between the exhaust manifold and the O2 sensor. All it takes is for that O2 sensor to see a little bit of fresh air and it tells your ECM to dump more gas in.

If your engine doesn't run like new after that then you have something else amiss, such as a faulty ECM, or a bad injector not working properly, or something else. Remember to re-set your ECM after installing the new MAF and O2.

Garyk 03-06-2012 04:48 PM

x-2 good advice.....to reset your ecm, disconnect the battery for a few minutes..

Xpress 03-06-2012 08:52 PM

Disconnect the positive and ground it out on the negative. It shouldn't spark or do anything, just drain the caps in the ECM, which is what resets it.

jdeere_man 03-06-2012 10:15 PM

This may seem to be a stupid point, but is your speedometer correct? If not (incorrect Speedo gear) your odometer is not adding miles correct. If you are figuring your gas mileage of an incorrect odometer that doesn't help.

deepak 03-07-2012 11:19 AM

yes the speedometer is correct.. thank you for your guys's advise

deepak 03-11-2012 11:42 PM

so i opened up the oil pan to replace main seal.. it seems like it's losing comresssiong :(

Xpress 03-12-2012 12:55 AM

Quote:

Originally Posted by deepak (Post 2113413)
yes the speedometer is correct.. thank you for your guys's advise

Are you sure? Did you re-gear the speedometer?

Z-TJ 03-12-2012 01:01 AM

Did you change your speedo gear?

deepak 03-13-2012 03:04 AM

yes the speedometer is correct.. i checked it with my gps...time to rebuild the engine.. gonna do the comression test then ill ask you guys if i have any questions..

miked196 08-23-2013 04:58 PM

x2 on the o2 sensor

banks316 08-23-2013 05:43 PM

Another thing that gets over looked...Engine temp... must be over 195 degree or the ECU stays in a closed loop mode. So heres deal on that. Your ECU has two modes close loop and open loop. Close loop mode is used for start up, it helps get the engine to operating temp buy burning more fuel and pretty much ignoring the O2 sensor. Open loop triggers when the engine is at operating temp. It then adjust fuel air mixture based on what the O2 sensor is telling it. There is a coolent sensor on the tstat housing that wouldnt hurt to replace. This sensor is for the ECU not the guage.

ddtt225 08-24-2013 01:09 PM

how can you tell by dropping the oil pan that your losing compression?

banks316 08-24-2013 01:10 PM

Quote:

Originally Posted by ddtt225 (Post 4115549)
how can you tell by dropping the oil pan that your losing compression?

You cant, you need a screw on compression test guage. It goes in the spark plug holes.

ddtt225 08-24-2013 01:22 PM

Quote:

Originally Posted by deepak (Post 2130130)
so i opened up the oil pan to replace main seal.. it seems like it's losing comresssiong :(

referring to his post guys. I know you cant tell compression by dropping the oil pan and that you need a compression tester. I was just trying to figure out how he knows he has low compression by just dropping the oil pan.

Matches 08-24-2013 05:47 PM

Quote:

Originally Posted by banks316 (Post 4113042)
Another thing that gets over looked...Engine temp... must be over 195 degree or the ECU stays in a closed loop mode. So heres deal on that. Your ECU has two modes close loop and open loop. Close loop mode is used for start up, it helps get the engine to operating temp buy burning more fuel and pretty much ignoring the O2 sensor. Open loop triggers when the engine is at operating temp. It then adjust fuel air mixture based on what the O2 sensor is telling it. There is a coolent sensor on the tstat housing that wouldnt hurt to replace. This sensor is for the ECU not the guage.

Backwards.

banks316 08-24-2013 06:26 PM

Quote:

Originally Posted by Matches (Post 4116094)
Backwards.

My bad... Thanks


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