Ok, so I posted about my terrible gas mileage, and got the usual "that's normal, etc". Well, i was looking today, and noticed some black electrical tape on one of the vacuum lines. Took the tape off, and this is what i found...could this be the reason for the terrible gas mileage?

This is the vacuum line that had electrical tape on it


And, here's the nice hole that was covered up with electrical tape



Obviously i'm going to replace that vacuum line anyway, but was curious if that could be the problem. Any and all help is greatly appreciated as always.

 

my guess is no. but im sure someone else will be along to give a more definitve answer.

 

Im saying no. That line is the crankcase vent system. Im no specialist but im saying No.

 

Anyone else? It runs from the intake manifold to the valve cover.

 

No but you should patch or replace the hose so the crankcase re burn will work right really all the crankcase system does is to re-burn the vapors so it really doesn't effect your mpg's.Check for header cracks that is a big problem and does effect mpg's.Try running some injector cleaner say sea foam or bg44 I think thats the name, or your choice of cleaner.Have you done a FULL TUNE UP on it lately start out with the simple things first gl.

 

I've done the following:
Air filter
Spark plugs
Plug wires
Installed Neon injectors
Oil change
Both diff fluids

I'm out of ideas. I know that with the amount of highway driving I do I should be getting more then 10. Especially considering how light I am on the throttle. But I'm out of ideas...

 

I just looked at a pic of your Jeep, I see it's lifted and has oversized tires on it. Have you re-geared your axles and/or changed your speedometer gear in the t-case? If you're trying to estimate your mpg without doing these things then you're way off base with your figures.

And to stay on topic, no that hole wont effect your mpg.

 

i had 32s with stock gearin on my xj for a while.....it said i was getting 10-12 mpg when in fact i was gettin 14-15mpg which is normal...my odometer was about 10% off

 

Well, i know the odometer is 10% off. If my odo says i've gone 200 miles, i've actually gone 220. That comes out to 11 mpg, instead of 10 and that still isn't right.

 

o2 sensors?

 

Well, i had a diagnostic scanner and it said they were fine. The test it did on my catalytic converter said "inc", i'm not sure what that means.

However, i just removed the downstream O2 sensor from the pipe between the cat & muffler to take a look at it. I started the Jeep without it, revved it a few times, and let it run for maybe 20-30 seconds. The CEL never came on. Isn't is supposed to throw a code? I didn't unplug it, just removed it from the pipe.

 

That hole on the CCV hose is from the cable on the hood rubbing against it. It shouldn't be affecting your mpg. I would however, either replace the hose, or put the tape back lol. Believe it or not, CCV hoses for our jeeps are somewhat hard to find. From my local experience at least.

 

Yea, I will be replacing that hose. Anyone know if removing the downstream 02 sensor should trip the CEL?

 

you said that you ran it for 20-30 seconds, which isnt enough time for the engine to heat up and switch from closed loop to open loop. generally a warm up cycle takes between 2-5 minutes so it wont necessarily set a check engine code

 

Do you think the sensor has ever been changed?