gas mileage [Archive] - GrandAmGT.com Forum

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cdm10700
01-22-2013, 07:00 PM
i have a 2000 GA GT 3.4 at. after i first purchased it, it got decent gas mileage and it seems like when it started to get cold outside last winter the mileage went down to about 12-15 if im lucky, i have changed plugs wires filters fuel pump temp sensor t-stat coolant tranny fluid filter and cleaned throttle body still doesnt seem to help. anyone have a solution for this anything something thanks

kzulfic
01-22-2013, 07:03 PM
Try any injector cleaners?

bricooper78
01-22-2013, 07:04 PM
Clean your Mass Air Flow sensor.

Does it smell like gas? Check engine light? Have you had it checked for codes?

BrittsBen
01-22-2013, 07:06 PM
I'm no expert but what can of air intake do you have? Sometimes vacuum leaks can cause loss of mileage.

Sometimes o2 sensors will wear out before throwing codes and affect performance.

Have you checked your tire pressure? The big tires on these cars can be deceptive looking.

Have you tried pulling your injectors and inspecting them?

I'd also check for fuel line leaks as the mileage you describe seems way off from what we've been getting.

Sorry if none of this helps, just trying to give back since this site has helped me.

klokworx
01-22-2013, 07:25 PM
Had an oil change recently? Run synthetic in the winter

bricooper78
01-22-2013, 07:28 PM
Britts--- I was going to bring up vacuum leak and CAI myself lol

cdm10700
01-23-2013, 04:52 PM
what is cai?
changed oil didnt try synthetic never thought it could help,
i only found one rubber vaccum hose it was cracked so i changed it,
i still have the stock air intake system, even ran motor without filter,
i have checked tire pressure several times, i did change both o2 sensors, no fuel leaks, i havent pulled the injectors but thought about it, guy i know said he could check to see if they are working properly,
cleaned mass air flow sensor,no light but did check for codes
ran several different types of injector cleaner thru it even had a fuel system cleaner ran on it
i think i will try the injectors themselves cant hurt
thanks for all the info

sleepyalero
01-23-2013, 05:33 PM
Cai = Cold Air Intake.

pauljs75
01-23-2013, 06:01 PM
I'll second the comment on tire pressure. I'm finding that the stock alloy rims on mine seem to leak air a bit, and moreso when the weather gets cold. (And the fact the car is over 10 years old isn't helping either. Might be some corrosion issues.) Low pressure is harder to notice visually since the tires are wider and lower profile than on most cars, but losing 5 psi, even if it doesn't make handling too mushy, can cause enough drag to noticably hurt fuel economy.

And this is a stupid one, but some people overlook it... No junk in the trunk? (If you really don't need to take whatever with you, leave it at home. Particularly the heavier items.) Also you're not frequently driving around some passenger(s) that may need to diet? You just might be the "good guy Greg" when it comes to helping out fair weather drivers.

cdm10700
01-23-2013, 06:40 PM
thanks, cai, im a little slow sometimes lol
tire pressure is right at 30psi on all tires and i have always had the extra weight in the trunk an usually its just me driving back an forth to work sometimes i have my 2 kids
what should rpms be at 55mph i think mine runs around 1700 1800
thanks again

bricooper78
01-23-2013, 07:32 PM
You don't smell gas do you?

Does it kick or buck when you're driving?

Shade2012
01-23-2013, 07:45 PM
You don't smell gas do you?

Does it kick or buck when you're driving?

I had a girlfriend like that one time.

kzulfic
01-23-2013, 07:51 PM
I had a girlfriend like that one time.

Did ya pull the ol rodeo style?

BTW, anybody mention FPR?

bricooper78
01-23-2013, 08:15 PM
Rodeo ftw

and thats where I'm trying to get to... wonder if it's crapping out and maybe flooding the thing a little, but it should act weird as he touches the gas from a stop/idle if so

kzulfic
01-23-2013, 08:27 PM
Rodeo ftw

and thats where I'm trying to get to... wonder if it's crapping out and maybe flooding the thing a little, but it should act weird as he touches the gas from a stop/idle if so

He should have some starting problems too.

bricooper78
01-23-2013, 08:34 PM
Yea, I'd think having to crank it when warm moreso than when cold, man most of this stuff is SO much easier to figure out in person lol

kzulfic
01-23-2013, 08:43 PM
Yea, I'd think having to crank it when warm moreso than when cold, man most of this stuff is SO much easier to figure out in person lol

I agree, even a video won't help much. I listened to that squeal of death one, and it just sounds weird to me with the lovely computer speakers, so I didn't even comment.

stewartfn18
01-23-2013, 10:39 PM
how about just the fact that its winter and the blend of gasoline is different.... i always saw a noticeable drop in MPG when i was up north in the winter. now, not so much

bricooper78
01-23-2013, 10:42 PM
But down that far? I've never had that low of a drop with winter blend, I honestly worried about the CAI dropping the mileage in the winter, but I haven't really noticed that either.

kzulfic
01-23-2013, 10:48 PM
how about just the fact that its winter and the blend of gasoline is different.... i always saw a noticeable drop in MPG when i was up north in the winter. now, not so much

I don't think it would cause that much of a drop. Last time I checked was late December, and I was still getting 28 with a mixture of city, and highway.

stewartfn18
01-23-2013, 10:50 PM
i saw usually about 20-21 city in the summer, and about 16 in the winter, so yes that much. also if you let your car warm up to operating temp that wastes gas when your not driving, and even if you dont you will still be driving in open loop for a longer period of time before the car completely warms up, more than in the summer, thus using more fuel

kzulfic
01-23-2013, 10:51 PM
Don't know why I haven't noticed it.

stewartfn18
01-23-2013, 10:58 PM
because seriously its been cold like twice this year. and i mean COLD, not 35 degrees

bricooper78
01-23-2013, 10:59 PM
man that's actually a good point, i didn't even remember the whole open loop garbage...

kzulfic
01-23-2013, 11:57 PM
Could be a mixture of the fuel, and air being more dense. Don't know, but I have never experienced that much of a drop the whole time I've had this car, or any other for that matter.

BrittsBen
01-24-2013, 03:45 AM
Do you buy cheap gas? Are you the original owner? It's really not that hard if you or someone who can help you that has decent mechanical knowledge to clean out your fuel injectors manually. Try any fuel injector cleaner? You may want to have someone vacuum test your fuel system for leaks if none of the easy solutions work. One good rule of thumb when in doubt is to find someone who can make an educated guess or conclusion and start with the cheapest things first if your going to guess. Keep receipts too and if it doesn't solve your problem, return it. If you don't have one already I'd say step one is to obtain a repair manual for your car.

cdm10700
01-24-2013, 07:37 PM
i havent changed the fpr yet
had same mileage all summer too
what rpm should it run down highway, i have noticed rpms vary a little on highway, not sure the number on tranny, its the one that doesnt have a dipstick

HenryM
01-25-2013, 05:46 PM
It could be a combo of more ethanol in the gas,,,also are you idling the car more in the morning as a warm up? The V6 is not very efficient in first 3 gears,,,,but once you are in cruise mode,,,you should be at 30 or better. My 99 with 232k, original trans and all, averaged 33 mpg with ac, 4 adults and some luggage to and from DC. My average for more city driving is 24 or so. But now with winter, colder weather has me idling a bit longer for the first warm up of the day, so my my average city mpg has dropped to 18 or so. BTW,,,my best average MPG was 38,,,I run Amsoil synthetic in the engine and the trans.

bricooper78
01-25-2013, 07:36 PM
87 octane, no ethanol FTW!

cdm10700
01-25-2013, 08:20 PM
i park in heated garage so it doesnt run to long in morning
so i should run 87 in winter?

bricooper78
01-25-2013, 08:24 PM
I have heard of condensation in ethanol from temperature changes, I think that was the cause, don't remember 100% why, but I've heard of the ethanol having water issues.

I run 87, mainly because our box trucks get about a 1mpg gallon difference on 87 vs 89, due to it being all gas instead of 90% gas..

I'm sure this is all debateable, but, I use 87 year round in everything I drive, with the exception of the camaro, that demanded 91, which comes with ethanol here by default.

btw, do NOT use ethanol in lawn mowers, it eats the rubber in the carb, so if you have dying mowers, there ya go, tech tip for ya :D

Roacho25
01-25-2013, 08:27 PM
what is cai?
changed oil didnt try synthetic never thought it could help,
i only found one rubber vaccum hose it was cracked so i changed it,
i still have the stock air intake system, even ran motor without filter,
i have checked tire pressure several times, i did change both o2 sensors, no fuel leaks, i havent pulled the injectors but thought about it, guy i know said he could check to see if they are working properly,
cleaned mass air flow sensor,no light but did check for codes
ran several different types of injector cleaner thru it even had a fuel system cleaner ran on it
i think i will try the injectors themselves cant hurt
thanks for all the info

During the cold months when your car starts up your fuel system will run on an open loop, until the point of your engine being up to temperature. Driving the car while it is in the open loop releases more fuel through your injectors to keep the car going. I suggest trying to let your car warm up a bit before driving it. I have monitors for various aspects of my GA and when i drive it without letting it warm up i get about 12 MPG

plastic_indian
01-25-2013, 09:52 PM
Before throwing more parts at it, verify the economy:

Warm the car up completely. Fill the tank to the automatic shutoff. Look for a decal on the pump indicating alcohol content, or ask the attendant (as if he'll know...) Reset the trip odometer. Go to the nearest highway and drive at a constant speed for 50 miles. Drive back to the same station. Fill the tank to automatic shutoff, noting gallons burned. Observe trip odometer and do the math.

Bear in mind cold engines use considerably more fuel. Cold engines that are idling to OT for 20 minutes in the driveway while the window defrosts every morning burn a lot more fuel than most drivers realize. Ethanol blends will deliver markedly lower economy.

Check trouble codes, diagnose and repair as required. If no codes, take a step back and look at the whole car: is a service brake sticking? Is the park brake messed up and sticking on? Is the trans shifting properly through all four gears? Is your buddy borrowing your car and beating the snot out of it on lunch hour every day?

cdm10700
01-27-2013, 09:30 AM
thanks for info i will try driving it a distance an see how it does
alcohol rating? should i look for a high content or low?
i did change front wheel bearings rotors pads rear rotors and pads - they needed changed wasnt just tring something
thanks again

stewartfn18
01-27-2013, 06:13 PM
why arent you running 87 all the time anyways

cdm10700
01-28-2013, 06:08 PM
have been runnin 87 ever since mileage dropped didnt see paying for the others when it goes thru it so fast

plastic_indian
01-28-2013, 07:45 PM
should i look for a high content or low?

All other variables remaining the same, fuels containing higher levels of ethanol will deliver lower economy -- ask a flexfuel vehicle owner how far off the mileage is on a tank of E85.

There is also some risk of damage to certain fuel system parts, although this seems to be a major issue only with classic cars and marine engines.