Perishing Gas Mileage?

I have a 2002 Taco Double Cab with the 2.7L in it. My gas mileage at the moment is at 14 MPG. When I first bought the truck a year ago I was hitting 17-18 in the city. Now does anyone has any clue why my gas mileage is taking a serious beating? It's been slowly declining over the last few months.

 

I notice my mileage start to dive around the time i need a service mine is a 2nd gen though

 

I'd tune it up to start with (air filter, plugs, pcv, clean MAF, oil/filter change, etc).
Then check valve clearances.
Do a compression check.
Check the resistance of as many sensors as you can.

 

first off, stop posting the same thread every 3-4 minutes and just wait for someone to help, thank you

now to the question:

can be lots of things but is the truck still running smoothly? any signs of power loss or hesitation?

when was the last time you replaced the air filter and changed the plugs?

a compression test is a good idea and the plugs need to be checked anyway to see if they are worn or wet with gas.

also check the engine oil level and smell it, is it higher then it should be or smell like gas? if so your injectors might be leaking

 

Possible O2 sensor. My mileage started decreasing before I got a CEL for a bad O2 sensor

 

Could likely be the O2 sensor. Changed mine for the hell of it and gained about 1.5 mpg.

The most common bad MPG reasons besides mechanical:

1.) Crap Gas, use High Tier Stations (Ethanol does not do your MPG's any good either)
2.) Lead Foot
3.) AC on constantly
4.) City driving

 

The site did that, not me. But thanks