ADK_XJ

Hey all, I recently filled my XJ up all the way for the first time in probably a few months since gas prices had gone up so high and then settled back down. I've eaten through half a tank of gas in 95 miles, mostly around town driving but that is still a pretty intense loss of fuel economy and I've noticed a faint smell of gas when I jump in the cab.

My initial reaction was a leak in the fuel tank, but I checked it over and it looks solid, plus I figure that would give a much more extreme drop in fuel level.

I've checked under the engine and along the fuel line for moisture or a more intense smell of gas and haven't found anything. Any ideas?

The only engine work I've done recently was an oil and filter change and I'd been driving for several hundred miles on that before I noticed the smell of gas.

98_XJ Sport

Has it gotten difficult to start after its been sitting for a while or sputter sometimes?

ADK_XJ

Nope. Just replaced the starter last month and still starting strong.

98_XJ Sport

I was thinking maybe a fuel pump? I smell gas in my cab too (haven't lost any mpgs) but that's where I am

ADK_XJ

Hmm, yeah I feel like the tell-tale sign is such a significant drop in mileage. 9.5 mpg is crazy bad compared even in the most intense driving I could do around here.

mikeoc1

If you know for sure your mileage since you filled up, fill it up again and see how many gallons it takes. Do the math and confirm your actually getting a mpg loss.

Wingnutz

I had the same thing happen to me on a trip a couple weeks ago. Mileage was cut in less than half. Ended up being the front O2 sensor.

ADK_XJ

Yeah? What'd that set you back?

NorCalJeep

Check your Oxygen sensor. Some of them can go up to 100$.

Wingnutz

Well, since I was in Cali and not back here at home I had a mechanic fix it for me. I didn't want to spend the time trying to figure out exactly what was wrong. Didn't have much time and wanted to spend it with family and friends. It was about $190 to troubleshoot it and to replace the sensor. I was kinda pissed since I just got a whole exhaust system with both sensors on it sitting back at home. Now I have a replacement for both.

NorCalJeep

Thanks for responding. Most people dont say if they fixed the problem.

ZINGGG

You must not be looking in the right places... And it's real simple to do yourself so no need to spend on labor.

ADK_XJ

You think it's quite a bit less for the 02 sensor? I'm still troubleshooting the issue, have 1/4 tank left and have done 150 miles. Something is not rihgt and I'm waiting for my next fill up to calculate the exact MPG loss...

RTorrez1

If you are getting the smell of gas in the cab. You might want to check you gas cap. Also check you fuel injectors. The injectors can be a little harder to find a leak on especially if it's a real small one. Just start her up and let it run until it's at normal operating temp and look for damp injectors. It's very unlikely that a leaking injector is the cause for such a MPG drop. But it may be the cause of the smell.
Good Luck!

ADK_XJ

Well, went down to Advance to get fuel injector cleaner, air filter and an 02 sensor to try knock out all possibilities - they ran their code on my check engine that just came on and said its a "gross leak" in the Evap system carrying unspent fuel back to tank.

Looks like this might be a job for a garage...