Horrible Gas Mileage...Help!!!!
10-12-2005, 05:32 PM
#1
Racer
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Horrible Gas Mileage...Help!!!!
I have a 96 LT4....so I filled up my tank full Sunday...its wednesday and I had to fill up again. I havent been gunning it or nothing. Running on the interstate to work in fifth and sixth gear. I had half a tank and went to reserve in one day going 50 miles. Im confused. When I went to fill up it made a loud hissing noise for a long time out of the gas vent before I opened it. Do I need to let the fumes out by venting the gas tank on a normal basis? Is that my problem? I only have a stock LT4 with corsa exhaust and just put on my open air box yesterday so I dont know if that could be it either....Help guys please.
10-12-2005, 07:18 PM
#4
Safety Car
[QUOTE=Achilleus07] Running on the interstate to work in fifth and sixth gear. .............When I went to fill up it made a loud hissing noise for a long time out of the gas vent before I opened it.QUOTE]
The hissing noise sounds normal...
On the interstate you should be pushing if not exceeding 30mpg......
Your are not explicit about what you are doing, but you should be in 6th gear on the interstate not 5th when you are cruising along.....the stock LT4 will run just fine at low rpm and deliver great economy..
The hissing noise sounds normal...
On the interstate you should be pushing if not exceeding 30mpg......
Your are not explicit about what you are doing, but you should be in 6th gear on the interstate not 5th when you are cruising along.....the stock LT4 will run just fine at low rpm and deliver great economy..
10-12-2005, 07:18 PM
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Racer
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I'm afraid it's broken - sell it to me cheap and I'll take care of it for you.
Seriously, if it were running rich enough to make a VERY DRAMATIC difference in gas mileage you would notice the poor running condition. I'd suspect a leak first and theft second, unless you park in a very vulnerable spot at night - then I might reverse that order.
Have you considered a failing guage? Maybe you have more gas than it indicates, and it's not a fuel problem after all. Of course then it would be an electronic guage problem - I don't know which I'd dread more.
The hissing when you remove the cap is a good thing.
Post the actual mileage, look inside the tank with a flashlight, check for leaks where you park / when it's running, and good luck.
Seriously, if it were running rich enough to make a VERY DRAMATIC difference in gas mileage you would notice the poor running condition. I'd suspect a leak first and theft second, unless you park in a very vulnerable spot at night - then I might reverse that order.
Have you considered a failing guage? Maybe you have more gas than it indicates, and it's not a fuel problem after all. Of course then it would be an electronic guage problem - I don't know which I'd dread more.
The hissing when you remove the cap is a good thing.
Post the actual mileage, look inside the tank with a flashlight, check for leaks where you park / when it's running, and good luck.
10-13-2005, 02:05 PM
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Im going to run over all the gas lines and everything today....I do smell some gas I dont know maybe I have a line leak....or maybe its just fumes we will see. Im running in fifth and sixth gear....mostly interstate driving and it still says im pulling 13 mpg....im thinking my gauge is messed up. Not alot of stopping nothing....sixth gear cruising at 70. When I do go slow im not peeling out....just regular driving...more interstate than city. We will see....im going to check the lines.
10-13-2005, 02:33 PM
#8
Melting Slicks
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Pull one of your sparkplugs and see if it's black. Also could be a bad O2 sensor - they don't always throw a code. My last tank, I got 11.8 city. It's back in the shop now for a free new chip and I told them to go ahead and replace the original O2 sensor.
10-13-2005, 03:57 PM
#9
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If either of your O2 sensors are delivering less than .5 volts at stoichiometric (14.7:1) then the computer wil richen up the mixture because it thinks the mixture is lean. This is a fairly common condition, and a cheap one to fix. If you have a shop with a tail pipe sniffer that can read A/F mixture, take it in and have it checked. If not, the spark plugs are a fairly good reading. They should be a soft grey/white, or perhaps off red color depending on the gasoline additives in your area. If they are black, and sooty looking, then you are probably running rich. Of course problems with other sensors can cause this as well. If your air intake temp sensor is bad, it could keep you are in warm up mode all the time. which also be quite rich.
I would put a locking gas cap on, and run a real MPG check, and do the math before I got too upset. And yes, the LT-1/LT-4 engines are pretty amazing when they are right. All that torque, and 30MPG's highway too.
I would put a locking gas cap on, and run a real MPG check, and do the math before I got too upset. And yes, the LT-1/LT-4 engines are pretty amazing when they are right. All that torque, and 30MPG's highway too.
Last edited by Dartvader; 10-13-2005 at 04:02 PM.
