So I know this is a common theme on here, but I am having sever problems figuring out why I am getting such bad gas mileage out of a 2001 4WD 2dr .
I have already done factory cap/rotor/plugs/wires (good to know peeps or factory would be way too expensive) Fuel filter, oil change, TPS, vacuum lines, brakes all around (no calipers or e-brake binding) tires at 35PSI and good tread, no 4x4 binding, no front diff hangups, no driveshaft binding, alignment is within spec, no MIL, cat is gutted, but has been for some time now. The only thing I have noticed, the fuel pressure KO/EO is at 58 and drops to 55 in less than 5 minutes. There is no washing inside the manifold and no smell of fuel. The truck makes a ton of power and has a GU6/3.42 ratio. Coolant temp is at about 180-190 and there is no stumbling or sputtering. There is a mild hard-start when the truck hasn't been run in over 24 hours only when cold. Any other ideas? I've owned many of these trucks, and love them, but even on my 92 TBI, I was averaging about 15-16 at 80-90% HWY, whereas this truck, I get 9-11MPG 80-90% hwy, and it doesn't change if I do 10% hwy and 90% city. This is the worst mileage I've gotten out of any car I have owned, Including a 600HP T/A. Any help would be greatly, GREATLY appreciated. I am hoping it is just something I overlooked and not something detrimental. Thanks for your help guys!

 

P.S. This just started happening 2 weeks ago. I know we have switched to the winter mix fuel, but I was getting 18+ hwy 3 weeks ago and now the mileage has been cut in half. Does NY just have really crappy winter mix

 

Do a fuel pressure test, rent a fuel pressure gauge from a local parts store, what it shoudl be at is easily obtainable from a simple search on the board.

PS, Does your oil smell like raw fuel?

 

When my gas mileage plummeted,a locking gas cap brought it back up.Damn neighbor was siphoning some once a week.

 

man thats some horrible fuel mpg! we were seeing around 12 all winter with our last one city driving and warm up idle, 4x4 allot.

 

Already did a fuel pressure test. KO/EO was 58 steady and dropped to 55 in about 5 minutes. No washing of the manifold or fuel odor. Neighbor isn't stealing gas because I watch the needle drop while driving to work and back. Thinking about just paying my local dealer the 150 to diag. This is insane!

 

I dont know why anybody didnt suggest this but I almost bet you have gas leak.Either a bad gasline or the tank is leaking.Crawl under it with a light and look around then follow your nose.

 

58 is low, it should be between 60 and 65 and not go below 55 for 10 minutes. You may have leaking injectors.

 

^^X2^^ 9-11mpg? Wow, I get 18 pulling my boat with a GU6!

Fuel pressure is low and that may be a factor. If an injector was leaking, it would show up on leakdown, which it doesn't. Coolant at 180-190 is low which can also affect fuel mileage. The thermostat starts to open at 195 and should regulate just under 200. Was that reading taken from a scan tool or the dash gauge? Have you checked the odometer for accuracy? Are the tires the factory original size?

 

Had the same thing happen to me with a Ranger. Tried everything including a brain transplant. Never fixed it so I sold it and bought a Tacoma.
Good luck.