My '04 Grand Am V6 is experiencing very bad gas mileage. It all started with a gas smell, which led me to replacing the Fuel Pressure Regulator because it leaked. I also ran some good quality injector cleaner through it. I had the plugs and wires replaced. Also just put in a new fuel filter.
STILL it has bad mileage. I don't want to put out anymore money until I at least have an good idea of what the problem is.

Any ideas?????

I read a Post on here that said changing the lower O2 sensor might be the problem. Does that sound logical?

How many miles on your 04 GA ??

Its quiet possible your O2(s) are the problem. You can test them first to see if they are working within range. Here's a link!
Oxygen Sensor- 99+ Grand am - Testing and replacement (http://www.automotiveforums.com/vbulletin/showthread.php?t=672110)

I just had the same thing go bad on my GA GT. Was getting 24-26mpg and then it dropped to 18-22. :( Replaced both and my mpg went back up and performance seems better too.

i had a 97 cavalier with the same problem but i did everything then one day i looked at my injectors, it they look wet or havr a stin around them thats your problem the orings seem to only take so much

O rings can be a problem, though you would smell fuel all the time.
Injectors in general are a problem with all automobiles.
If you dont keep them clean they'll clog and cause problems including bad MPG.


and Welcome to AF bigmeat8 !

I have the fuel smell problem fixed. It was the Fuel Pressure Regulator.

I'm going to change the lower O2 sensor and see if that fixes it.

also one thing that people overlook most of the time is dragging brakes. If your GA is not coasting as it used to do before when you let of the gas it could be that your brake pistons are not retracting back enough.

I checked the brakes and they are not dragging. I'm having them changed anyways tomorrow cuz they are getting worn.
I had the O2 sensors checked and they are fine. Also, while it was hooked up to the diagnostic computer, everything else checked out fine. So dead ends there. The mechanic suggested that I get gas somewhere different than where I usually get gas. I also am running some more good injector cleaner. Hopefully the combination of good fuel and cleaner will clear up the problem of gas mileage. :uhoh:

I had the O2 sensors checked and they are fine. Also, while it was hooked up to the diagnostic computer, everything else checked out fine. So dead ends there. The mechanic suggested that I get gas somewhere different than where I usually get gas. I also am running some more good injector cleaner. Hopefully the combination of good fuel and cleaner will clear up the problem of gas mileage. :uhoh:

Are you refering to the cleaner that you empty into your gas tank...... if so thats great but the problem i find with that method (unless done from day 1 and on a regular basis) is it gets diluted too much and isn't really effective against heavy carbon build up.

I would suggest a full fuel injection service such as Motorvac etc

I've just started using the Terraclean system which i'm having some really good results with so far and its much more healthy for us techs running it :grinyes:.

Are you refering to the cleaner that you empty into your gas tank...... if so thats great but the problem i find with that method (unless done from day 1 and on a regular basis) is it gets diluted too much and isn't really effective against heavy carbon build up.

I would suggest a full fuel injection service such as Motorvac etc

I've just started using the Terraclean system which i'm having some really good results with so far and its much more healthy for us techs running it :grinyes:.

:iagree:
BG also makes a very good kit.

The downstream O2 sensor will only affect gas mileage by 10%, so that's probably not your only problem.