What could be the problem? Lead foot? I also vibrations from 65-75 on the highway around 2500rpms (automatic). After 80 my car gets smoother. Could it be Fuel filter? Could it be that one of my plugs are fouled?

 

I am a newbie, but according to what I've read in this forum, I can point several possibile points.

For poor gas milages:
1) dirty TB, MAF or air filter. Clean/replace them.
2) dirty spark plugs. Replace them.
3) O2 sensors, maybe?
4) dirty transmission. replace or even flush tranny.
5) possible knock sensor.

For the vibe:
1) Check wheel balance. IMHO, it's nothing to do with engine system.

 

got my wheels balanced if it were wheel balancing it would get worse as speeds get higher 80+ it smooths out cruising at 100 is smoother than 65-75.

 

20mpg is good if your hitting 100mph IMO. Im getting 19mpg w/ mainly city driving. I do have lead foot and a knock sensor code.

 

hmm true, i do tend to drive a little aggressively on the highway i'll make note of that. thanks i'm going to try to replace my spark plugs, air filter, and fuel filter, (in that order lol)

 

damn i wish i got 20mpg i get like 15 maybe lol damn i love to drive fast

 

Something I have noticed about most of the complaints(threads) about getting 20 mpg and under is that they always seem to be from NY or NJ. Maybe the eastcoast gas is crappier than the rest? MN gas isn't the best either but not THAT bad!

On a road trip a while back I noticed that mileage went way up(30mpg) in Illinios, Tennessee, Kentucky, Georgia, and Florida. I have never seen that kind of mileage in MN. 25 if I'm lucky.

 

Maybe we have worse air too but I just bought this car a month ago and found out it didn't have its 60k tuneup

 

Or maybe us in NY/NJ love to go 0-60 on ever stop light and traffic jam? That 10% ethonal probaly dosent help either.

 

[QUOTE=whitegold]Or maybe us in NY/NJ love to go 0-60 on every stop light and traffic jam[QUOTE]

i know i do

 

All gas is the same as it goes through the US Pipeline. The oil companies put their additives and marketing to make them different. The 10% ethanol has some impact on MPG but not too much.

When was the last time you got a tune up? You could have a ghost Knock Sensor code, or your o2 sensors could use replacing.

Take the car to an alignment shop, it could be your alignment or your wheel is unbalanced.

 

Well i'm pretty much in either stand still traffic or stop and go traffic and i manage to squeeze over 21mpg with a very very very heavy foot. I hate NY so damn much.

 

I have the lovely ghost KS code (i have one sitting in my glove box too lazy to stick my hand in there) and im pulling 18-20mph.

 

This is why I no longer drive during the day, only late at night to avoid trafic!

 

unfortunatly nothing is wrong with your car. 20 mpg is about the average. you figure thats pretty good for an older 3 liter V6 that wieghs 3000 pounds.

 

i already got my stuff aligned like i said if it were alignment the vibration wouldn't go away at 80+ mph. Tune-up I dont know. What consists of a tune up. I had the engine oil changed and I plan on changing sparks, fuel filter, and transmission fluid.

Whats a ghost code? I checked my ecu (with no cel) and I got 5,5 (no failure recorded/detected).

 

Try running premium gas with injector cleaner, and de-carbon you intake track.

-Andrew

 

I'm usually getting that kind of mpg. I heard some people changed there O2 sensors and getting better mpg, cause the air fuel ration is a lot better.

 

I did do fuel injector cleaning addiditve. De-carbon intake track = throttle body cleaning? Maybe we'll see. I just changed my plugs and the car feels SO smooth. The shudder is gone and i think acceleration is better. I used iridium plugs how long do they last for?

 

Iridiums are about 8-times stronger than platinums, so they should last at least twice as long or more. I would check them every 30K, whereas platinums should be replaced at 30K. I believe iridiums, as long as they are not fouled, could most likely last the life of your engine. I do not, however, feel that they perform as well as platinums (in my own engine, my own experience).

 

clean your tb... im from ny and i cleaned it a couple months ago... did wonders the car is a lot more responsive... anything above 65 in any car you will def see your gas mileage go down... i do about 20-22 with mixed city/highway

keep it at 55-65 youll start seeing 25-30mpg again if you have no codes

 

ooh. Well to me it feels like they're a lot better than my old ones. You dont miss what you dont know so i dont think i'll be changing to plats just because they're better in a sense.

I will clean my throttle body, is it difficult to do yourself? Or should i get a shop to do it.

 

With 50/50 mix highway/ city driving, I get about 20 mpg using 89 octane gas from speedway religiously (from a FULL tank, I get 290 miles to a quarter tank remaining). I have new plugs, Clean filter w/ Short ram, 300z ffilter, Ypipe and UDP, Trans fluid is changed once a year. I don't use synthetic oils, but use lucas twice a year. I drive 20,000 miles a year though and have a moderately heavy foot. Youngstown, Ohio has ok gas (it does have ethanol in it). The car pulls slightly to the right, but allignment is on (according to the shop) and I have NO excessive tire wear. I also have a slight vibration at 55-70 mph approx and do not know why, tires are new (1 year old). All other drivetrain is OK, I gave a thorough look over (cv's, brakes, new control arm bush and sway bar bush). Tires are at 34lbs. I also cleaned the TB about 3 months ago.
-Oh, and the car is waxed with Eagle One 'Wet' so its extra slick for the wind stream (lol)

 

DO NOT pay for a shop to clean your throttle body. That is silly, if you'll excuse my frankness.

There are four screws and a couple of harnesses to remove, a few hoses to unplug, and the throttle cables to disconnect. If you remove your throttle body (which is very easy), you will be able to clean it easier because you can clean both sides, as well as portions of the manifold itself. This is a great DIY project for a newbie or any experienced DIY org visitor.

 

wow i wish i could get 20 miles to the gallon. i average about 280 miles from full to empty with the light barely coming on. i do mixed city and highway driving, and i'm code free. that equates to about 17.5 miles per gallon (280/16) and i don't drive fast at all.