Dramatic Change in Gas Mileage 2005 Vibe Base Auto

[LSchaferphoto]

I've had my 2005 Vibe base automatic for over a year now. The first year I consistely got 32-33 mpg with 87 gas. Now I consider it a good day if I get 27. No codes, no lights on dash. Regular oil changes with synthetic only. Any ideas on what could be wrong?

[star_deceiver]

How many miles? Any changes in driving, more city - less highway? Tire pressure?

[ehoff121]

There are other maintenance items that could adversely affect fuel efficiency.

You didn't mention changing the air filter.

Have you ever run a bottle of Chevron Techron fuel system cleaner through a tank? Partially clogged fuel injectors could be a contributing factor.

Also,

Are your driving habits the same?

Has your mix of city/highway changed?

Is the A/C on for the same amount of time/frequency?

[LSchaferphoto]

No changes in driving habits or city/highway ratio, air is on a majority of the time but that isn't anything new. (I live in FL it's always hot!) Car has 63k miles, K&N filter, tire pressure is 32. Will try fuel system cleaner. Thanks for the advice!

[Salsa Guy]

There is a gas station that everytime I filled up the MPGs dropped by 3-4. Needless to say we don't use them anymore. Running some fuel system cleaner isn't a bad idea and ofcourse check the air filter and piping (someone had a mouse nest in the air filter box). May even try resetting the ECU/PCM.

[joatmon]

viewtopic.php?f=17&t=6088&#p65128" onclick="window.open(this.href);return false; has an excerpt from the factory service manual on the things to check if mileage is lower than expected

[CharlesinGA]

No changes in driving habits or city/highway ratio, air is on a majority of the time but that isn't anything new. (I live in FL it's always hot!) Car has 63k miles, K&N filter, tire pressure is 32. Will try fuel system cleaner. Thanks for the advice!

Clean your mass air flow sensor with approved cleaner, and get that K&N filter out of there. The filter is wetted with oil, the oil gets on the MAF and affects its operation.

Other possibility, but not likely with such low mileage and synthetic oil is the filter for the variable cam system, could be clogged. This is known to kill mileage with no other effects.

Charles

[vibenvy]

Clean your mass air flow sensor with approved cleaner, and get that K&N filter out of there. The filter is wetted with oil, the oil gets on the MAF and affects its operation.

I agree about cleaning the MAF sensor and ditching the K&N filter. Check out aFe for drop in filters that do not require oiling (Pro Dry S).

[Salsa Guy]

Another area that maybe worth looking into is the O2 that's located on the exhaust manifold. The o2 sensor has the last word on the fuel control and if the reading is off it will cause the engine to run rich and reduce the MPGs. They are about $70 and you'll need a special O2 socket (about $10). Make sure you get a quality OE fitment, Denso makes the O2 sensors for Toyota.

[ehoff121]

tire pressure is 32

Might be a difference between base and AWD models, but check the spec on the door- I think fronts are supposed to be 35 psi...

[Sparkeyoo7]

How many miles do you have ? It could be very possible you are due for a plug change iridium plugs are recommended and good till 100,000 miles or 160,000 Kms but I wouldn't go past 60,000 miles or 100,000 kms hope this helps....

[CharlesinGA]

How many miles do you have ? It could be very possible you are due for a plug change iridium plugs are recommended and good till 100,000 miles or 160,000 Kms but I wouldn't go past 60,000 miles or 100,000 kms hope this helps....

No changes in driving habits or city/highway ratio, air is on a majority of the time but that isn't anything new. (I live in FL it's always hot!) Car has 63k miles, K&N filter, tire pressure is 32. Will try fuel system cleaner. Thanks for the advice!