I just got back from a 400 mile trip pulling a car trailer with atoyota 4x4 with a v-8 in it. My truck got 6 miles to the gallon and had no power. I have 4.56 gears,power programmer, k@n,and 35s. with a 318,new cat and exhaust .Is their anything I can do to help this sick goat.Its even underpowered with no trailer.

 

6 mpg is bad. start with the most common problems. you did the cat. check into pre-cat 02 sensor, tune up, plenum gasket. also check for gas in your oil (leaking injector). you didn't mention your towing speed..... these things are not very aero, so above 60 its a declining curve.

 

60 was not even an option. I had to go around 50 to 55. The tranny seemed to be working fine. It acted like ithad no go to it.I did a tune up before I left.I did look in the throttle body and it looked real nasty. it seemed like dry gunk. but did not see any oil.Im only getting 10 without a trailer.Its not burning oil and i checked for oil in the fuel. but did not detect any. this truck has 130,000 on it

 

ok, so you've already done tune up (plugs, cap, rotor ?, maybe wires). cat. transmission seems ok. speed is slow, not excessive. no noticable gas smell in oil, nor thin oil, nor increasing oil level. you have big tires (35) but have regeared to 4.56.

how much lift you got (that hurts aero and mpg) ?
what rpm's are you turning at 55mph (OD off and OD on) ?
are you towing with OD on or off. just asking because its generally not a good idea to tow with OD on unless you going real fast.

i'm still thinking you might want to check into pre-cat 02. also check plenum. do a seach for about a million posts (take a look at mine). but generally a leaking plenum is simply an internal vacuum leak, causing a lean condition, pinging, lack of power, minor or major oil consumption. generally the larger the oil loss, the worse it runs. i'm thinking that your problem is excessive fuel use, rich condition (maybe o2) and probably not plenum. someone please correct me if that seems wrong.

 

I have a 5" lift . I never tow with overdrive. I regeared so at 55 with od on it runs about 1800. and with a trailer it is around 2800 with od off. But i did check some of the other topics on here and noticed. it dosent really kick down until i floor the truck. So i wonder if i might have a tps bad.Then if i change it and reset the computer. due i need to remove my programmer info. so it is not lost

 

mine had very poor gas pedal response that improved with new tps. it wouldn't expect it to change your mpg any, but it sure does drive better. your rpm's are close to mine. with no lift, stock 3.55 gears, slightly bigger tires, i turn 1500 at 55mph w/OD on and about 2100-2200 w/OD off. you don't really want to hear this but i get about 13 city (OD off) and 15 hwy (OD on) and not towing. i haven't done any long haul towing to know what that mileage would be, but i do have to really put my foot in it with the boat hooked up.

 

I'm leaning towards plenum ... excessive oil usage isn't always a symptom. A bad pre-cat O2S should throw a code.