jrivas162

I'm trying to figure out why my car is getting 10MPG, I know its a V8 but i also know its supposed to get around almost double that, any suggestions of what the most common problems would be? I talked to a dealership and they told me tire pressure, O2 sensors and cats. I don't know what else it could be that i could check or do myself.

Boris91

Fuel filter, spark plugs, lead foot lol.

FlamingoGT

What's the maintenance history like? What is your driving style like? auto or stick? How is the alignment? How are the brakes? What kind of gas do you use?
Ask me again in a few weeks and I should have better numbers myself, but in the city I get about 15 mpg and straight highway driving I only get about 22 mpg. But I also know I need to get the plugs replaced and change the oil. And an improved tune would probably be a good thing too.

cliffyk

As O2 sensors age their output drops, the output voltage range of 0.2V to 0.8V narrows, and the output at 14.7:1 AFR (normally 0.45V) drops to 0.4V--not enough for the PCM to report it as bad, but enough that the PCM's injector pulse width calculation will be incorrect and the engine runs rich¹.

If the front O2 sensors on your 2000 GT have never been changed then they would be the first thing I would suspect in a poor fuel economy situation.


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¹ - A low voltage signal from a P-Z O2 sensor indicates a lean mix--so with an aged sensor producing lower than proper voltage the PCM thinks the mix is lean and incorrectly richens it resulting in poor fuel economy--read more about P-Z sensors here.

jrivas162

@FlamingoGT - Alignment is good, brakes good, auto, no lead foot lol, the previous owner had "all scheduled maintenance himself" except for the last 2 oil changes and tire rotations before trading in to the dealer. Use regular Shell Gas and tried some SeaFoam and it helped just a touch, could feel a lil better improvement on acceleration.

@CliffyK - Yeah I was thinking about getting a tune-up either way so I think I'll just grab some O2 Sensors for the fronts and have them changed.

Thanks for all the input guys Ill try it out and keep u guys posted.

kast1376

FWIW, I had a cat that was starting to clog that I had to swap out and changed the fuel filter made a huge difference. I average 17mpg around town, and 22-30 highway depending on how much traffic there is.

jrivas162

so by any chance is there a way to clean the Catalytic converter on the car or even removing it from the exhaust?

cliffyk

They cannot be cleaned, but can be removed. You will need MIL eliminators to turn off the SES lamp, and trick the I/M monitor into giving the emissions systems a clean bill-of-health (require by inspections in many states).

If you live in a state that visually inspects for the converters you will fail emissions testing. In one that actually "sniffs" the tail pipe you may fail, maybe not if the engine is hot when they test it--drive it at highway speeds for 20 miles or so before going for testing.