So i just filled up my gas tank today and i figured out i get about 11-12mpg just driving no wheeling. well it idles ok but it gets rough sometimes. any ideas?

P.S. i just did a tune-up. new dist. cap, plugs, wires, intake, and all fluids.

 

Fuel filter or injectors clogged?? Never mentioned these in your tune up list. Have you run a bottle of fuel system cleaner through it recently? Rough idle can mean vacuum leak, also. If you cleaned the engine in your tune-up, you could have gotten water in the distributor.

 

have you tried seafoam? i haven't used it yet but I've heard good things and will try it soon

 

i pressure washed it before i changed everything so there isnt any water. i did a fuel system cleaner but i think im going to change my fuel filter tomorrow. It kinda sounds like its missing but idk how that could be. Hopefully a new fuel filter will fix it.

 

Im also going to change out the map sensor and o2 sensor. I think i should be good then.

 

take the throttle body off and clean it real good with carb cleaner... after i did that mine idles much smother and i got like 60 miles more out of a tank.

 

so i got an o2 sensor, a map sensor and seafoam today. any last thoughts of what it could be

 

what rpms does it idle at?

 

around 750rpms.

 

My new 89 was idling at like 500 so I put about 1/2 tank of premium in it and it brought the idle up and runs smoother. I have found that regular gas nowadays with the ethanol in it is not very good and running plus in our 04 Corolla I can get about an extra 50-100 miles per tank. I've heard from others that have Jeeps that Plus or Premium makes them run better due to the poor quality of regular gas these days.

 

Posibley a crank position sensor ,

 

Intake Air Sensor should get a thourough cleaning.

This sensor tells the computer if it should enrichen the mixture due to temperature fluctuations.


IAT is located:



Sometimes the MAP sensor vaccuum and the IAT are reversed.


This sensor when removed should look like this:



There is a small diode inside the plastic cage that SHOULD be BLUE.

Due to its location, it probably looks BLACK. This is from the oil soaked air the CCV is pulling from the vavle cover. This oil coating makes the IAT give a false temperature reading, thusly poor performance and MPG.
Remove from intake, give good cleaning with brake cleaner and re-install. That easy.

ALSO: What does your air filter look like?
Like many XJ's, its probably oil soaked. This comes from the CCV breather tube. You need to turn plastic portion of the tube. Rotate until the bend closest to the vavle cover is in the UP position. The idea is to create a hump in the tube.
This doesnt stop the oil getting to the filter, but alleviates alot of it.

 

thanks

 

Well i cleaned the throttle body and the iat. Installed my o2sensor, fuel filter, and map sensor. Let see if this helps the gas mileage. Is there any way u can put the CCV so it doesnt go into the intake, maybe a breather filter?? let me know

 

should of done each thing one buy one to trouble shot your problem so u kno what was wrong