really crappy gas mileage

Hey I know that I am not a big poster on this site but I try to help out when i can. I was hoping someone would have an answer to this question. My car has 127,000 miles and the engine is still in really good condition, however the thing sucks gas like you wouldn't belive. When i got the car last feb. i would get around 300 miles to a tank. Now all of a sudden i'm getting 150 to a tank. WTF is with that? I had it hooked up to a scan tool and it showed a lazy o2 sensor so i replaced that and this is the first time i am testing the mileage out on a full tank. I come up with 200. Still not satisfactory in my book, when my dad's 95 grand prix is getting 300 miles to a tank. Can someone please tell me if maybe there is a coolant temp sensor that might go bad and be causing really shitty mpg.
Thanks

is your air filter clean? also the way you drive the car can make a difference in what kind of milage you get....

I bought a brand new K&N air filter changed the fuel filter and also changed the plugs and wires.
I live out in the country so I do drive with a heavy foot but is that enough to make the milage change that much?

possibly, just depends on HOW hard you drive it.. i used to drive my car hard when i got it but never got that bad of mileage. i normally get about 275 miles to a tank doing a LOT of city driving, and that's with mods. i dont know a whole lot about diagnosing fuel problems...could it possibly be fuel injectors maybe being stuck? .. just a guess

This question comes up a lot on the national board. Try this: http://www.clubgp.com/newforum/tm.asp?m=1190427&p=1&tmode=1&smode=1

I know that you're car is a GTP but some of the suggestions still apply.

ok thanks i'll take a look at that

ok thanks i'll take a look at that

Have you ever had your injectors cleaned? Does the car take a little more time to start in the morning?

That may be your problem right there...

Change the pcv valve if you have not done so recently...and check your tire pressure...

All three of these things can effect mileage a good bit.

Have you replaced your plugs and wires?

Yeah I have replaced the plugs and wires, I did a pretty basic tune-up when i got the car including coolant flush and stat, plus the o2 sensor now. I haven't had my injectors cleaned which gives me a thought, and haven't touched the pvc vavle. Tires are always well inflated. Cars got 127k on it so I'll try just about anything at this point. I'm also going to try taking it easy on the gas pedal and see if that helps out a good deal:)

smell your oil on dip stick if theres gas in your oil it maybe your fuel pressure regulator seen this a few times

also pull the vacuum line off of the fuel pressure regulaor if theres gas in it you found your problem
an expensive one to boot get a used one for a car with that many miles

yeah there is a gas smell on the dipstick but i'm not even sure were the regulator is. Isn't it under the plenum? I take classes at the tech school so i'm not that illiterate i just dont know were the regulator is.

the regulator should be in thr rear of the plenum
you can get to the vacuum line with a long needle nose plierse
it should look like a beer keg with vacuum....HAHAH
if you cant get to that pull other vacuum lines and smell them
if thers a strong gas smell in your lines its a very good indication of the problem
also pull the boot off your throttle body and check for gas
also smell your exhaust for raw fuel smell
you ask about coolant censer maybe but it wont make it use fuel that bad and change your oil soon