1989 F-150 4.9L I-6 hp and mpg

Jacobus03 · #1 09-18-2006, 04:56 PM

I don't really have the time to search through everything on here so I figured I'd just throw this up. I have a 1989 F-150 with the I6 and 5 spd OD trans, 4x4, reg cab long box, just turned 70,000 miles today. I get about 10 mpg and it just feels like it's really weak. I have been working on changing parts when I have the time. Just the small stuff for now, plugs, wires, filters etc...and no improvment in mpg. Also are there any bolt ons that will improve my hp? that won't crush the wallet. I was pulling a trailer today going 70 on the highway and I hit a hill I dropped 25 mph and had to go down to 3rd gear and it really wasn't that big of a hill, and the trailer was empty and it's not heavy, I pull it with my 2.9 ranger easily. I am not real familiar with this Engine so any help or previous experiences will help and are greatly appreciated. Thanks in advance.

john finley · #2 09-18-2006, 06:48 PM

I also have a 89 F150 except i have the 5.0 v8 but I have been looking into new airintakes ive heard from a couple freinds of mine that put a performance intake on their trucks that they got a couple mpg extra and acceleration had really improved on one but im not a mechanic so dont hold me to it

RaWarrior · #3 09-18-2006, 07:07 PM

"Cheap" and "horsepower" just don't go together. Don't fall for claims to add 20 hp with a $50 bolt-on, they're all bogus. Aftermarket air intakes can improve hp, but by maybe 5hp at the very best and a tad more fuel economy, and only the "good" intakes do that. If it came from wal-mart, it's not a "good" intake. Even for the modest gains, expect to pay easily $200.

10mpg is very poor. I have a '93 2 wheel drive with the same motor and same trans, and can get 20 on the highway pretty consistenly, maybe 12-13 in town.

If the engine also seems to lack power(the 300 is known for it's high torque) then chances are something's wrong, espically if it only has 70k on it. People here have ones with over 200k still going strong. Towing clear up to a ton is nothing, you will barely even notice it. I've pulled an 800lb jetski and not even felt it behind the truck, I've even gone up decent hills still in O/D and the motor barely even slows, easily maintaining 65. Without a trailer I could drive up Everest and still not need to take it out of overdrive.

If you can find it, look for K-100 fuel treatment. Honest to God, it's the only fuel additive I've ever used with noticable results and actually does what it claims. It's tough to find and expensive ($8 for like 12oz) but it works. I ran it through one of my sleds that had some bogging issues and wouldn't reach WOT. Carbs needed to be cleaned, but one of my buddies recommended K-100. I'd always been skeptical of "mechanic in a bottle" fixes, but within 10 minutes the bogging reduced and was gone by the end of the tank, and WOT was almost instantly restored, no kidding. Opened the carbs, so clean they were shiny. Made a believer out of me. Dump a bottle of that in your truck, it'll certianly help with the ****-poor performance.

Jacobus03 · #4 09-18-2006, 07:27 PM

thanks for the help K-100 huh, I'll look around for it. I can tow very well with the truck, I hauled a Ranger on a heavy bobcat tralier and then a Saturn on the same trailer shortly after, today, they follow great and truck moves good with that, but it was the uphill with no load that really bugged me. I tried some seafoam but I think i need to put more in the truck, I only did about 1/3 of a can, but I'll look for K100 and see if it works. I know the $50 bolt ons with 35 hp gains are BS, and mechanic in the bottles some seem to work and some don't. A friend of mine had the same truck except his was a extended cab, He was getting 16mpg average, with cith and hwy driving, I'd be happy with that, but getting only 200 miles to a full tank of gas just hurts. The truck is all stock too, well except the tires, they are 30" and the truck also has 2" blocks in the rear. I'll keep trying stuff and see what happens. Thanks for the info

Atipsword · #5 09-18-2006, 10:31 PM

When I bought my truck it ran like crap, bucking and stalling, and felt like it had about 20 hp. I bought a bottle of Gumont All in One Cleaner from Wal-Mart and after one tank, it fixed my whole problem. It's worth a try and it's only $5 down the drain if it doesn't work.

94f1504.9 · #6 09-18-2006, 11:21 PM

i have a 94 with the same motor and trans but i have 33" tires and it still doesnt do too bad on gas, well that is for a lifted truck.

RaWarrior · #7 09-19-2006, 07:06 PM

I used some Gumout cleaner in my truck the day I got it since it had this lag just off idle, which made getting going in first kinda a hassle. Seemed to help, but the tank's almost gone and there's still a noticable bog, but I've also gotten better at driving it's tranny so it's not really a problem anymore. I'll put k100 in, if I can ever find it. One shop near me gets some in about once every 80 years and it always sells out very quickly(even the mechanics use it as parts cleaner).

Nathan Plemons · #8 09-20-2006, 10:48 AM

Sounds like a clogged catalytic converter to me.

Jacobus03 · #9 09-23-2006, 05:24 PM

hmm never thought about the cat, i'll have to check it out tomorrow and see, i'm in WI maybe i'll just cut it out and straight pipe it. I'll let ya know

Bruce R Leech · #10 10-16-2006, 10:54 PM

well what happened

Jacobus03 · #11 10-26-2006, 12:37 AM

Quote:

Originally Posted by Bruce R Leech

well what happened

Nothing I haven't gotten to it yet, had some other stuff come up that is more important. My dad and I need to fix the front axel since I broke it last year when I got the truck stuck so no 4x4 now, he said we'll check the cat then, need to do it soon starting to get snow up here. And it's getting down to 20 deg at night. brrrr. I also found a 95 F-150 with the 300 and 5 spd for $1995 wiht 111,000 miles reg cab sb 4x4...think I might pick it up, sweet blue color some rust...but overall a nice truck.