4.0 Need Help Bad

[PhdNPrerunners]

Yesterday I bought a 97 4.0 4x4 with a 160k miles ranger for 1500. So I drove it from dallas back to houston and when I was on the freeway it seems like it would jerk for a sec then be fire and it would do it like every 20 mins. On the way back the truck got horrible gas mileage. I barely got 200 miles out of a full tank. Do you guys have any suggestions? Thanks

 

[Big Jim M]

If I just purchased a vehicle that was 10 years old I'd be out there under the hood changing the plugs, wires, caps, rotors, coil, fuel filter and anything else such as the air cleaner that I didn't know if it needed it or not.. I'd start her off fresh so I'd know when the next time she needed attention would be..
Chances are after refreshing her she will run correctly once more.
200 miles on a tank is a silly statement to make!! Did you put 10 gallons or 16 gallons in that tank? EVERYONE should be capable of computing their gas milage at EVERY fillup!
DO IT! Every tank, compute in your head what your milage was. It becomes quite easy after a few tanks.
Big JIm

 

[PhdNPrerunners]

i put 16 gallons in it. I think the bad gas mileage might be cause the truck has 31s on it and it has 327 gearing. So im thinking of changing the gearing to 373

 

[Big Jim M]

i put 16 gallons in it. I think the bad gas mileage might be cause the truck has 31s on it and it has 327 gearing. So im thinking of changing the gearing to 373

If I'm not mistaken there was a 20/25 mph head wind yesterday from Dallas to bigH.. That would cause you a few mpg all by itself.
I run a later model 4.0 4X4 with 4:11 and 31" tires I get 19 everyday with the A/C on high.. 2WD with 3:73 should get equal or better if you drive it like an old woman, as I do..
Big JIm

 

[PhdNPrerunners]

If I'm not mistaken there was a 20/25 mph head wind yesterday from Dallas to bigH.. That would cause you a few mpg all by itself.
I run a later model 4.0 4X4 with 4:11 and 31" tires I get 19 everyday with the A/C on high.. 2WD with 3:73 should get equal or better if you drive it like an old woman, as I do..
Big JIm

Ya the wind was really bad. Im sure the speedo is off a little bit. My truck is a little single cab 4x4

 

[PhdNPrerunners]

Do you guys think that 373 will be a good set up with 31's and 4.0 5spd?

 

[kunar]

i would go with 4.10's cause youre not gonna hurt anything and youre only gonna regret not going deeper next time youre looking for tires. if your speedometers off, than your odometer isnt right either.

you should be able to find an entire axle with 3.73's or 4.10's in a junkyard for cheaper than buying the gears alone. the swap is much easier this way.

 

[Big Jim M]

Do you guys think that 373 will be a good set up with 31's and 4.0 5spd?

Since I don't intend to ever use taller tires, I actually think my 4:11 is a bit too low. Although I havn't used a 3:73 with my truck I think I would be happy with that ratio. At hiway speeds my rpm is around 2600. I'm thinking every little bit helps and a few less rpm would still keep me in full timing and lean mixture. (economy)
But if you are in doubt go for the 4:11's... I'm here to tell you the lil truck runs fine and has lots of low end with em.
Big Jim

 

[fireguy12117]

as big jim said, the best thing to do would be a basic tune up, unless you have a better history from the previous owner? i purchased my first 4x4 from a guy that was a single owner and had every receipt for all the work ever done, so i had that history. an intermitten stumble at speed on the highway could be a number of things. was there a check engine light ever?

 

[PhdNPrerunners]

When all the lights on the instrument panel come on when I start it I dont see a check engine light.

 

[AllanD]

If I just purchased a vehicle that was 10 years old I'd be out there under the hood changing the plugs, wires, caps, rotors, coil, fuel filter and anything else such as the air cleaner that I didn't know if it needed it or not.. I'd start her off fresh so I'd know when the next time she needed attention would be..

<snip>

Big JIm

No cap or rotor on a 4.0 and a coil is prohibitively expensive to
be replaced casually, as it's a "six pack" coil-pack assembly.

The LIKLIEST coil related problem with a 4.0 coil pack (or on other EDIS equipped Ford) is corrosion inside the high voltage terminal and most tool companies make a special brush to clean them out.

IF on startup you DO NOT see the "check engine" lamp light up
I'd first check the continuity path for the light bulb between
the lamp, power and the computer (The lamp is grounded
through the computer)
IF the Check engine lamp is simply removed from the instrument cluster the late EEC4 computers and ALL EEC5 computers will run the engine in "limited strategy" and create the symptoms observed all by itself.

Ditto for a light bulb that is simply burned out.

Likliest thing is that there was a check engine light lit for some inconsequential problem and someone removed the bulb to "hide"
the problem so they could sell the vehicle.

So the VERY first thing I'd do would be verify that there is a bulb
in the proper socket and that it's good.

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