inferior fuel economy on '99 LE V6

[krayziazndragon]

just recently (past month or so) i've noticed that my 1999 Camry LE 3.0L V6 has been delivering inferior fuel economy.. after a friend pointed out how quickly my fuel tank needle was dropping, i started really keeping track of my miles.. i checked all the specs and after averaging several trips to the gas station, it came out to be around 16 or 17 miles per gallon.. too far off from the 22 mpg / 28 mpg city / hwy estimates and too close to the 15 mpg i get with my 4.0 Liter explorer.. i drive A LOT of fwy so i dont know why this is happening.. just for testing sake, i drove at my most fuel efficient speed as much as possible and accellerated no more than 2k rpm (except on freeways) for the most part for 2 whole tanks.. still inferior fuel economy.. i plan to get it looked at in a week or so.. any ideas on what i should probably be looking for? thanks everyone..

[cycosurfer]

My friend had a similar problem, although it was on his Honda Accord I'm sure it applies here as well. His oxygen sensors had gone bad and it was getting him the same mileage you are talking of. Once he got those replaced, he had gone back to the glorious 28++ mpg his old volvo gas guzzler could no longer compare to.

[ProMan]

The first thing you can do is to check the engine error code to see if there is any code stored. If the Ox sensor is bad, your check engine light will lit and there should be a code related stored in the computer.

[Mike Gerber]

First do what ProMan said. Get the codes read. Autozone will do this for free. If there are no codes present, I would still check the coolant temperature sensor (Toyota calls this an ECT sensor) with a DVM. It may be defective and telling the computer the car is always cold. This would produce a rich mixture all the time, wasting a lot of fuel. You will need to get the specifications from a manual for this. This too should throw a code, but I have seen instances where they are defective but do not throw a code for some reason.

Good luck.

Mike

[krayziazndragon]

would it still read a code if the check engine light is still off?? cuz it never went on.. ok so pretty much just the oxygen and coolant temp sensors? anything else i should be looking for? thanks soo much.. --michael

[Mike Gerber]

The check engine may have come on for an instant and then gone off when you were driving and didn't notice it. The code should still be stored in the computer's memory until erased by a scanner. That's how OBD2 cars work.

As far as other things that could cause poor fuel mileage, the slightest bit of brake drag on any of the wheels would greatly effect mileage. You can jack up each wheel (or the entire front or back end if you have a floor jack) and see how hard the wheels are to spin by hand. Leave the emergency brake off when checking the rear wheels. If you find one wheel that is noticeably harder to turn than the others you have found the culprit. I would, however, consider the other things first, although this is something you can do yourself without any special tools. It's up to you.

Good luck.

Mike

[Toysrme]

In order:
Reset the ECU - Pull the EFI switch out, count to some small number and put it back in.
If it continues check the o2 sensors for the corect output, and check the long & short term fuel trims.
Clean the upper intake
Give carefully cleaning the inside of the AFM a try