03 grand am gt horrible fuel mileage

**SteveCZ28** · 08-07-2010, 09:38 AM

got some questions, or need some help in this area. my wife has a 03 grand am gt with the 3.4 liter in it. has 90k miles on it. we took it on a trip last week and i noticed how horrible it is on fuel mileage. we took it on a trip which was 200 miles and it literally took over 3/4 of a tank of gas to get us there. so i filled the car up and reset the trip and drove ti to see how far it will go on a tank of gas it will go 285 miles on a tank of gas until the low fuel light comes on....even my maro will go 200miles on half a tank of gas. so im puzled as to why we cant get the mileage out of it. the car isnt thrwoing any codes at all, doesnt spit,sputter,shake or shutter, so i dont know where to even start here. any ideas would be helpful at this point

**Smittro** · 08-07-2010, 09:57 AM

Originally Posted by SteveCZ28

got some questions, or need some help in this area. my wife has a 03 grand am gt with the 3.4 liter in it. has 90k miles on it. we took it on a trip last week and i noticed how horrible it is on fuel mileage. we took it on a trip which was 200 miles and it literally took over 3/4 of a tank of gas to get us there. so i filled the car up and reset the trip and drove ti to see how far it will go on a tank of gas it will go 285 miles on a tank of gas until the low fuel light comes on....even my maro will go 200miles on half a tank of gas. so im puzled as to why we cant get the mileage out of it. the car isnt thrwoing any codes at all, doesnt spit,sputter,shake or shutter, so i dont know where to even start here. any ideas would be helpful at this point

You could try some CRC on the MAF, then do plugs and wires.. I'd still take it and have it scanned.. Could be a intermittent code that's not triggering the SES light.. Cat could be starting to crap out too.. I hate sequential injection.. Batch fire (tuned port) was so much more reliable back in the day. Maybe change the MAP sensor too... They don't get the greates mgp's to begin with tho but that does sound off a bit.. I get roughly 300 miles from a tank of premium in the 3800 Camaro.. You should do @ least a little better than that tho with less cudes and the 3.4 ohv being a more efficiant engine in general.. Check tire pressures and brakes for maybe a slight hang.. That's all I can think of right now.. Let me know if you need more help, I can dig into the manuals if needed..

**SteveCZ28** · 08-07-2010, 11:46 AM

yea i did all the brakes all the way around 2 weeks ago...left rear rotor/pads were shot, but for it to still have shitty mileage is beyond me...ill clean the maf, and see how that is, and maybe pull a few random spark plugs and see how they look

**SteveCZ28** · 08-07-2010, 12:10 PM

cleaned maf, and checked plugs. pulled all 3 in the front they look new, as in they had been serviced recently. and they all had fresh grease on the boots

**Smittro** · 08-07-2010, 01:01 PM

Well you prolly did the air cleaner then too. I'm @ a loss @ what could be causing it.. I think you should be getting between 22-24ish mpg's or better so there has to be something we are missing here.. Maybe try some injector cleaner. Could even be water in your tank, bad batch of gas

just guessing @ this point.. Could be a trans issue starting.. Is the converter locking up like it should ? (if you noticed) Or shifting right? I'm trying to come up with a possible cause.. But

is there any noticable power loss when cruising? Any highway speed bucking or misfiring?

**SteveCZ28** · 08-07-2010, 04:29 PM

yes checked the filter, it was clean...i knocked some of the loose stuff out (bugs, bigger particles and what not) doubt theres water in the tank as its been getting shitty mileage for a while (wife just told me, i just noticed on the trip we took) transmission still acts fine, doesnt hold gears longer than it should, doesnt slip, doesnt bang into gear when actually shifting it into gear, and doesnt have hesitation either when putting it in gear. torque converter still locks up just fine. and locks up when temp gauge is about 1/4 the way up everytime. no power loss when driving, doesnt spit or sputter at highway speeds either, and still plenty of power when u stomp on it, will light the tires up

**SteveCZ28** · 08-07-2010, 04:30 PM

Originally Posted by SteveCZ28

yes checked the filter, it was clean...i knocked some of the loose stuff out (bugs, bigger particles and what not) doubt theres water in the tank as its been getting shitty mileage for a while (wife just told me, i just noticed on the trip we took) transmission still acts fine, doesnt hold gears longer than it should, doesnt slip, doesnt bang into gear when actually shifting it into gear, and doesnt have hesitation either when putting it in gear. torque converter still locks up just fine. and locks up when temp gauge is about 1/4 the way up everytime. no power loss when driving, doesnt spit or sputter at highway speeds either, and still plenty of power when u stomp on it, will light the tires up

its funny that my z28 gets better mileage, and has 126k on it. im getting anywhere from 315-375 per tank in it

**Smittro** · 08-07-2010, 04:31 PM

Originally Posted by SteveCZ28

yes checked the filter, it was clean...i knocked some of the loose stuff out (bugs, bigger particles and what not) doubt theres water in the tank as its been getting shitty mileage for a while (wife just told me, i just noticed on the trip we took) transmission still acts fine, doesnt hold gears longer than it should, doesnt slip, doesnt bang into gear when actually shifting it into gear, and doesnt have hesitation either when putting it in gear. torque converter still locks up just fine. and locks up when temp gauge is about 1/4 the way up everytime. no power loss when driving, doesnt spit or sputter at highway speeds either, and still plenty of power when u stomp on it, will light the tires up

You got me then.. Can't think of any other reason for the crappy mileage...

**SteveCZ28** · 08-07-2010, 04:32 PM

weird...might just clean it up and sell it then

**Smittro** · 08-07-2010, 04:33 PM

Originally Posted by SteveCZ28

its funny that my z28 gets better mileage, and has 126k on it. im getting anywhere from 315-375 per tank in it

Gets better mileage than my 3800 too.. I get about 300 per tank full of premium..

**Smittro** · 08-07-2010, 04:39 PM

Originally Posted by SteveCZ28

weird...might just clean it up and sell it then

Maybe try a couple tanks of premium.. That's about all I got..

**Y2KPewterSS** · 08-12-2010, 07:04 PM

Originally Posted by SteveCZ28

uhm wow....thanks for completly steering my topic off course..i made this for help on my wifes car, not to hear what everyone else gets for mileage

Cleaned up, lets keep this on the original topic to help the OP.

**02convertibleT/A** · 08-30-2010, 10:55 AM

i owned a GAGT for a while. had a 2000 GT Coupe. MPG was around 17 average. 20 highway. i wasnt getting more than 240 when the low light came on.

Dont forget, if you dont know already, about the intake gaskets.

even after my tune up. PCV, Plugs, Wires, Belt, it was getting the same gas mileage.

i miss that car. that car was gettin the chicks in high school!!!

**SteveCZ28** · 08-30-2010, 11:38 AM

havent figured it out...were gonna try to get the car paid off here real quick, then unload it somehwere

**02convertibleT/A** · 09-01-2010, 04:28 AM

Originally Posted by Smittro

That body style put the GAGT back on the map. imho best body style ever offered..

my favorite style also!!! Pontiac did good with the Grand Am and Prix. The wider body stytles really hit the mark! i miss the car, hes selling it and i wouldnt mind getting it as a back up car, and a winter car for my GF when we store the mustang. i got so much azz in that car back in high school. haha. but, i had to stop playin sports to pay for it, and i was on track to a very nice baseball career. So i can basically say it kinda ruined my life, but it was my own fault. shouldve stuck with my 92 2.2L cavalier that was a tank and stuck with baseball. (enough of my rant) lol.

although a G6 coupe with the 3.9 is pretty sweet!!!! E-shift, nice lookin dash, and leather! not a huge fan of the GXP styling with the big grille and spoiler.

**transamgirl89** · 09-06-2010, 12:00 AM

Originally Posted by Smittro

Probably your best bet I hate to say.. The 4t60e and the 4t65e are junk trannies right out of the box.. It may soon bite you.. The differential areas of the case are weak and will sometimes let the diff bind and out comes the CV joint or it may even start to toast a wheel bearing as a sign of internal trany problems I mentioned.. Also the friction material used is anything but good from the factory.. Even the HD units are super weak.. Ask meh how I know dis..lol

Agreed there! The tranny is horrible on these cars. My mom has a 99 GA and it's on its second engine with the original transmission. It has around 135k on it and for some reason if you cut the wheel to sharp the low track light comes on and the tranny starts slipping. It completely misses 1st gear from a dead stop but it only does it randomly. If you haven't replaced the transmission do it now before it goes out like smittro said.

**SteveCZ28** · 09-07-2010, 03:41 AM

wow, i love all the stories yet again, that in no way shape or form help me with the indentification of my crappy fuel mileage...

**Smittro** · 09-07-2010, 04:44 AM

Originally Posted by SteveCZ28

wow, i love all the stories yet again, that in no way shape or form help me with the indentification of my crappy fuel mileage...

Posts removed....

Good luck in your quest for mpg's....

**stonemason90** · 09-07-2010, 10:07 PM

the 3400s get horrible gas milage once they hit 50k miles.... when i had my 2000 GAGT1 it only got 16 mpg... and like yours there was nothing wrong with it.... oh and it only had 106k miles when i sold the car....so not far off what yours is....

edit... its a common problem with grand ams... they get bad gas milage....really nothing can fix the problem except getting a 4 cylinder.... lol

**Smittro** · 09-08-2010, 04:29 AM

Originally Posted by stonemason90

the 3400s get horrible gas milage once they hit 50k miles.... when i had my 2000 GAGT1 it only got 16 mpg... and like yours there was nothing wrong with it.... oh and it only had 106k miles when i sold the car....so not far off what yours is....

edit... its a common problem with grand ams... they get bad gas milage....really nothing can fix the problem except getting a 4 cylinder.... lol

Umm what??