Hey I am new to these forums and I have a question. I am sure that this has been asked before, but I am getting really bad gas milage on my '94 Dlx 3.0L V6 4x4. I'm getting about 12-13 Plus or minus mpg Highway. No I have replaced and tuned the following

-Brand new Cat
-Brand new oil filter
-Brand new Fuel Filter
-Brand new Air Filter
-Brand new Mass Air flow Sensor (Ouch $$$$$!!!)
-Brand new Clutch (done less then a week ago)
-Brand new spark plugs
-Brand new spark plug wires
-Adjusted the timeing to 12-13 DFTDC

Truck has 140k miles on it and I have 265/75/r16 size tires. Now for the sob story. I have had it in and out of the shop now 3 times, the mechanics have told me that it's in perfect mechanical condition. But I step on the gas and there is no power, I go up a small hill and I'll lose speed by about 5 mph e.x. going 75mph it will drop to 70pmh or below. Now I live in Arizona and it's flat here not to many hils so I don't have harsh driving condition. Can someone please help me figure out what the hell is up????

 

By process of elimination the only thing you haven't checked or replaced is your ignition system. Plugs, Cap, Rotor, Coil, Wires... O2 sensor is also a likely culprit, if you're running rich you'll have bad power and even worse mileage. Good luck in finding the problem.

 

sorry i forgot about all that. Ya that was some of the first stuff I changed.

 

try going to advance auto parts and request to use thier OBD scanner you'll have to establish if its OBD 1 or OBD 2, i know the 98 taco is OBD 2, basically its a free way to get a diognostics check, they will explain how to use it. to my knowledge advance auto is the only one's that do this. i hope this helps.

you might also check into Vapor Lock, where the fuel line get warm enough to cause the fuel to evaporate befor it hits the intake.

again hope this helps

 

What gears do you have and what tranny type? That sounds like the problem, unless you just neglected to mention that you changed your gears.

 

to be hones I don't have a clue as to what I want trany I have. I looks to be the stock one. And as for gears I haven't changed them, but I baught the truch with 16" rims and 265/75 size tires on it and I was getting 17+ mpg. I don't mean to shot down any of these ideas or anything, but I figure the more I tell everyone the better I can get some help on this. PLease keep the ideas flying at me!!

 

did you try the OBD scanner, i used it ofr a couple of "check engine" problems

 

Ya no codes that I can see and no check engine light at the moment. This is why I am stumped as to why I am getting such bad gas millage.

 

I'm not sure what the problem is if you were getting 17, but from this:

it sounds like you don't have the proper gear ratio for those larger tires. I have the same problems with hills and I have the wrong gears in my truck.

What I meant earlier about tranny was do you have an Auto or a manual....

I can't say for sure, but I would check your gear ratio or ask who you bought it from what gears it has, but it would be more reliable to check yourself.

From the looks of it, it's in perfect condition as far as the engine, so that's the next logical step.

 

Oh ok I see what you mean. Um well it's a manuel 5 spd. Do you know where I could get new gears and how much would they cost?

 

if you step on the gas will it get up and go, or is it sluggish when at operating temp? if it is try when its hot, check the fuel lines if they are excessively warm or hot, that may be your problem. any stock gear toyota puts in the truck are capable of turning 32" tires at 33"minimum 4:10 better 4:56 or 88. my 1st sgt has a 92 with a 3.0 running 32x11.5 on his completely stock truck, but i'm not a toyota tech

 

It won't be exactly cheap, but taking the differentials out and taking them into a shop to have the work done saves some labor costs. Someone with more knowledged on actual gear stuff will have to chime in on that stuff. And you can order them online, lots of sites.

 

Yes that is exactly my problem I step on the gas when it's the engine is at normal op temp and it's freaking slow. Like nothing undr the hood. I will have to look at feel the fuel lines. I would have never thought about that. Does anyone know why the lines could get so hot and how I could fix that in the future?

 

just try some insulation tape, similar to what is on headers,my 98 taco had the same problem, vapor lock, but you could tell the fuel lines were hot.

 

Just took a long test drive and the fuel lins were fine no hotter then anything else on the vehickle. Still will probably do the tape thing but I found this on the web http://www.bobblick.com/techref/proj.../o2sensor.html I wanted to see what you guys think. I know that i don't have a dodge carovan but the syptoms are the same. LMK

 

did you try the OBD scanner yet? too bad wasn't the fuel lines thats an easy fix with the tape.

 

no My obd is an OBD I and the auto part stores dont have that out here anymore. Because they all went to the OBD II type I would have to buy the scanner. It's like $150 just for that.

 

Our trucks dont use scanners, just count the flashing engine light when you short the test terminals. I made the mistake of buying a scanner for a 90's toyota once, it was a wire with two spade terminals, in a box, for $30.00!!! I returned it.

 

well too bad, wish you luck.






it's better to say nothing and have people wondering how stupid you are, than to open your mouth and remove all doubt.

 

hitman, hit up derrick090 he seems to know something about these problems.