Csmith

1991 runner 4wd, auto 3.0 has just been rebuilt got over 1400 miles on it now, but MPG is still 10-13 The best is all highway. Is this normal, I would feel better with 16, my tahoe does better with much more power. Does Auto tranny have alot to do with this. have tried advancing timing, no change. Seems to run fine though in all situations. What gives, any help would be great. I think any mods I make will just make it worse. Thats no load condition

Csmith

searched around, it's typical - haven't changed fuel filter yet.

AgRunner06

Replace your O2 sensor. That ought to help it.

Yoter

What all did they replace? What grade of fuel are you using? What promted you to rebuild it. I have a 91,4x4,auto,203K,and get around there also. I plan on replacing it but not sure if the Vortec by Chevy I want to replace it with will slip in or need major mods.

kaiberg

join the club my man...3.0hh how sucky can the gas mileage be V6...if i fill up and get on the freeway...i can get about 280 miles before i better find a gas station....yeah the first 2 gen's are definately pigs:pig: ...ohh well gotta love em anyway right

Yoter

How many miles can you go on a tank of fuel? I make it around 140 miles on a full tank using Chevrom or Safeway brand mid or supreme. I bounce depending on what I used the fill up prior. Dont ask me why I just do.

Bumpin' Yota

My 3.0 is getting on average 17mpg. High is 21 low is 15 currently and I have a dead O2 sensor. Prior to that it was getting 24mpg high and 16 on the low end. If your milage is that bad, something is wrong. How hilly is it there? When did you last swap out your fuel filter and O2 sensor?

Steve

mycotopian

I get about 200 miles per tank with isr mod and fresh head gaskets

L33T35T 4Runner

steve, i have no idea how you get that with the 3.slow. i have NEVER heard of anybody get anywhere near those numbers

kaiberg

my thoughts exactly man...i just did the math and im content with the 16 im getting after hearing of lots of guys getting 10-13...how in the hell are you clocking in at 24 ??????

Yoter

I kinda forgot to say I only get 140 miles to the tank due to 35" TXR tires. Rigs tend to work harder to turn that BIG of a tire I think. I changed my fuel filter and had a full tune not long ago. O2 sensor huh? Do they go bad often? I figured when that would go out my check eng. light would come on. Hmmmm!

Bumpin' Yota

The high numbers are from highway driving here in FL at 65 mph. (speed limit is 70) We have NO hills. I also run 225/75r15s or 235/75r15s, nothing larger. Im really thinking that the O2 sensors need to be changed often on these trucks....

I can't really help it if other people aren't getting the same milage, perhaps my toy is the exception....

Then again mine will run ~100 on flat ground if the air temp is below 80F, most 2nd gens can't do that. I dunno why other than my mods, I just know based on this truck.

AgRunner06

My best is 21 on the highway with the windows down. I would say I probably average between 14 and 16 combined now. I try not to get over 3k rpms when I drive. I baby it.

Although I've never heard of 24 mpg before. Your truck must be a freak of nature.

Do a tune-up: plugs, wires, rotor, cap, fuel filter (if it has never been done), O2 sensor, and put a can of injector cleaner in there. Then see what you get. I've done all those things.

Bumpin' Yota

The 24 was on one tank. At the time everything was stock save a KN airfilter. I was running 225/75r15 BF Goodwrench T/A Trail 4 plys. On that trip I did not gun the engine at all again 65mph in a 70 zone. Never gotten that milage since....dunno

Robinhood150

Check your AFM. That went out on mine and the mileage went way down and no check engine light.

cabbage

About the 24 mpg... and you were on a trail... did you get stuck a lot?? would spinning the tires cause a high mpg?

Bumpin' Yota

no trails, I already gave full info about the 24mpg...

But for clarity, Ill go over it again was on I-75 in florida on a sarasota to gainesville commute, I don't remember any wind, I did not gun the engine one single time. 65mph the whole way, engine turning at ~2400rpm. 225/75r15s. A/C off. No system, nor any extra weight from one at that time. Me and about 20lbs of books and clothing.

If I go on the trail for any length of time, I get about 10mpg or less for that tank...


Now back to the topic. Swap out the O2 sensor, fuel filter, do the ISR mod, check the AFM vane, clean the throttle body, check plugs, plug wires, cap, and rotor, check the engine timing, possibly replace the cat with a free flow cat, and think about a 2.25" exhuast system and new muff. I have NO clue if headers would help or hurt.....

mycotopian

Robinhood

Where is my AFM located and how do I know if its shot?

Csmith

Well -rebuild was due to worn out rod bearing when I bought. I did rebuild and put in all new rod,crank, pistons, etc.

New cap,rotor,same wires though. Thoroughly cleaned throttle body. Timing is advanced a little maybe 8-10 degrees.

I average 150-180 miles on a full tank.

I will change fuel filter, check O2, and AFM.

I did put a drop in K&N, all bilstiens & leveling spacer,but all else is virtually stock.

Sometimes idle drops to 500 at stop and auto tranny shifts hard on occassion - changed out those fluids 2.

runs pretty strong though - for what it is -Solid offroad
got gas

doink

lucky, i cant seem to break 200 lately, but then again, that is city driving