I have a 1989 F-150 custom, manual transmission, with 91K miles. It’s my first car. I am 16. We just got it over the summer. The guy we got it from had done a bunch of work on it, but he’s a family friend. Lately, as it is driven more, its been having several problems, including:
- Sticking idle control(it idles at 3000rpm and is also there when in neutral)
- occasionally it starts, but the turn signals and heater don’t work. The signals work when the engine isn’t on, but once it’s turned on, they don’t. However, the hazards work all the time. I went over a bump when this was happening, and both the signals and heater started working.
- this happened for the first time tonight. It has front and rear gas tanks. I keep the rear filled. I was filling up the front tank at the station, and once the tank got full(or close) gas started leaking from the truck. The pump didn’t stop pumping. I tried again and it did the same thing. The gauge says it’s at full tank, so maybe an overflow valve somewhere? This is a safety issue and a waste o’ my money.
- would I get better gas mileage if I shifted to a higher gear from low or high rpms? Ex. Shifting at 1500 or 2500 from 2nd to 3rd?
Since I am 16, and don’t know much about engines yet, should I try to get help and fix these myself or take it to a garage?
Wow - however much duct tape you have, get another couple of rolls.
Here are a couple of things I can suggest. First, by the sounds of it, you should dump the truck before you think about taking it to a shop - this is a money pit if you have to pay someone else to work on it. There will be occasional things that you would need a shop for. But in general, you will go broke and fast for routine stuff.
Find an older friend or relative who has done a bunch of work on cars to talk to & ask questions of. Preferably this would be someone who is willing and able to help you out on actual repairs. Nothing compares with an actual experienced person sitting there with you giving guidance & tips.
Also, for $20 you can pick up a basic repair manual for this truck at an auto parts store. These are bare bones kinds of things, but they give you the basics. You can get a wiring diagram for the hazards and blower motor, for example, along with the basics of electrical testing and such. It will give you things like procedures for removing the gas tank if it comes to that (just sounds like a leak - don’t use that tank). If you can splurge some more find an actual factory shop manual - way better, though not as user friendly.
Never ever ever skimp on safety. Do not put that truck up in the air - ever - and get any part of your body under it without a good quality set of properly rated jack stands. Other stuff laying around won’t do - especially things like concrete blocks. They are death in the waiting. Get a good set of safety glasses - use them. An assortment of gloves are handy too. Use the internet at will. You might be surprised at what kinds of car work you can find people doing on youtube.
I agree with everything cigroller said.
Especially the first sentence.
I switched tothe rear tank. The guy we got it from replaced one of them. I’m just not sure which. So the tank might just be bad. But I’ve topped it off before, and it hasn’t happened. And do you mean to make sure the car won’t move while working on it? Because there’s over a foot of clearance under it already.
As for the Internet suggestion, that’s why I came here first!! Old guys and old cars in the same spot. In truth, the guy who we got it from did say it was a good car to learn engines on because of the basics of it. No computers or anything. I love learning engines, and would take the whole thing apart, but I don’t quite know how or have the tools. Also I live in Cincinnati, and it is snowing right now, so working on it might be a little hard.
And we won’t get rid of it that easy. We got it cheap, and I need a truck for doing yardwork. Plus isn’t that what your first car is supposed o be? A piece of junk? 
I agree with everything cigroller said, now onto the questions at hand.
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High idle may be due to a dirty throttle body or IAC (Idle Air Controller). The $20 Haynes or Chiltons manual can show you how to remove each. Use a good throttle body cleaner to clean these out and any air passages in the mounting body.
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You have and electrical problem, likely due to a dirty or damaged connector somewhere. Electrical problems are time consuming and a lot of fun (/sarc, yeah, right). Start at the fuses for each of these and work your way to each electrical connector under the dash feeding the circuit.
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The front tank has a major leak. This is either at the filler neck connections or the sending unit seal. Do you need both tanks? I’d avoid using the front tank until you can afford to have someone look at it to determine the leak. Hint, the tank may have to be dropped to determine the problem. Don’t put anymore gas into the tank until the leak is fixed, and get the gas you do have in it out as soon as possible. Gas fumes are very flammable and this type of leak is allowing gas fumes to leak out and collect under the truck bed. All it needs is the proper fume to air ratio and a spark. If you don’t have a good method to siphon the tank, use the tank as you drive around to empty it as soon as possible.
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This truck will NOT get you good gas mileage. It is a very heavy, V8 powered behemoth. However, keeping the RPMs as low as possible without ‘lugging’ the engine will get the best possible gas mileage short of using hyper-miling techniques. At best, you should see 13-15 mpg if this truck was in perfect tune.
**PS, Just saw your post after mine. Originally this truck had a fuel-injected engine. If it is a carburetor, the engine is not original, and neither is the fuel system. A high idle means the carburetor needs work. Hopefully just a cleaning and adjustment. At worse, a rebuild.
Ok so get the gas tank empty ASAP an keep it that way. Then get someone to look at it. I know a few people who might be able to help with that.
The electrical should be something affecting both units, so something behind the dash maybe? I’ll pobablt end up getting a wiring thingy and try to fix that.
It has an idle control mechanism right on the op of the engine block. It was replaced recently, so maybe it’s jut sticking?
And I was told it was only a 6 cylinder, 4.9 liter, but was told they never made that size, so I’m pretty sure it’s a 5.8 liter, but I’ll check the piston number
As for gas mileage, I was only told it gets at best 13, and I’m still learning how to best drive it, so I get about 10 right now.
In general, for best gas mileage the ideal spot to be is in the highest gear possible where you aren’t lugging the engine (it doesn’t chug or bog). But as noted, for this truck it is lipstick on a pig.
Other than than the most important things about gas mileage are to keep good tires, properly inflated, good alignment & suspension, a well-functioning cooling system, clean filters, plugs & wires.
Perhaps when the idle control mechanism was replaced someone had their eye on the wrong thing? Was it idling high before that? High or fluctuating idle is usually about air leaks - whether vacuum line leaks, intake leaks, or idle control mechanisms.
These kinds of vehicles are great to learn on though if you had a choice I would have suggested a small 4 cylinder truck.
A lot of clearance or not there will be times when you need to get it up in the air. By all means do anything you can with all 4 wheels on the ground. Other than that you’ll want a properly rated set of ramps, a floor jack, and jack stands.
And who are you calling old? Punk. 
Yeah, if it is the 5.8L and not the 5.0L, your looking at 13 mpg tops. The 4.9L V6 was a joke. Less torque than the 5.0L, and marginally better gas mileage, meaning not enough to notice.
BTW, I wear my greying hair as a badge of honor. Now, get off my lawn!! 
Haha why the hosts of the show, of course!!!
Ok I’ll look into it. But why would it over flow only when the tank was completely filled up? And only today. It just got really cold here. Could temp difference have cracked something or broken a seal?
Ok so I looked it up. It’s a 4.9 liter, 145 hp inline 6. And my dad ain’t got hair already, so don’t mind me. Besides, older folk need more yardwork.
So if I get 12 mpg hauling stuff around, I should be happy.
The tank has a seal at the top where the sending unit/fuel pump assembly bolts to the tank. The filler neck and vent line also attaches to the tank with rubber hoses and clamps. Either one of these could be cracked and leaking. Being rubber, cold weather will cause the rubber to shrink, forcing cracks to widen and open. Given the truck is 22 years old, old cracked rubber seals and hoses are not uncommon.
If you get 12 mpg in city traffic with ‘stuff’ in the back, you’re not going to see much better. Completely empty, you may see 13 mpg. As I said, this thing is a thirsty behemoth.
Ok I’ll look at it. It’s probably a busted seal due to large temp differences in a short time. And I think it is the tank that wasn’t replaced, so it’s possible. I’ll be careful driving it and look at it next time I can feel my fingers. Also, another question or two.
- the truck doesn’t have a plug in for towing a trailer to operate the lights. If I’m working on the electrical, should I also put one in? Are the hard to install? I would use it for hauling a trailer with lawn equipment or my scout troops trailer, which needs the lights.
- even though it’s a smaller engine, it’s still decent. Would it be big enough to pit a small snowplow on the front? Like one for doing driveways in only a few inches. Nothing commercial size.
Oh and rubber is like water. It actually expands as it gets colder. Could it have expanded enough to come loose and not make a seal?
Just out of curiosity, how solid is the truck, as far as the body and chassis? How rusty is it? Up here in northern Ohio we don’t see many of these trucks anymore because they all rotted out. If you haven’t already, give it a thorough inspection, paying close attention to body mounts, suspension mounts, bumper mounts, floor boards, seat/seat belt mounts, etc. If the truck’s structurally sound, what you’re experiencing isn’t too bad for gremlins that will show up in a 22 year old truck…and you’ll learn a lot about basic mechanics with this tank.
Don’t worry about trailer hitches and plows yet…get the truck up and running and try to work through all the issues with it. But if you must…If the truck’s not a 4x4 a plow is out of the question, and besides, most people will tell you that a manual trans is not ideal for plowing. Trailer wiring harnesses are a cinch and most are plug and play off the rear tail light harness. Don’t tow anything heavy with a ball mounted on the bumper; you need a legitimate trailer hitch.
You turn signal and heater problem could be a sticking ignition switch. When you turn the key to the right to start the engine, there is a spring inside to return the ignition switch back to the “run” position. If that spring gets weak or the part that turns gets corroded or dirty, it may not return far enough to make contact with the part that sends power to the turn signals and heater blower.
The next time it happens try turning the key slightly left and see if that makes things work. If it does, just get in the habit of doing that.
For the gas leak I’d check the rubber hose going to the filler neck, they often crack or split with old age. 10 MPG, I can hardly afford to drive a car that gets 40 MPG. The only car I ever had that got 10 MPG was a '76 Lincoln Mark IV with a 460 CI 4BBL, but gas was only $1.00-$1.25 a gallon then. The next worse was a '75 Ford LTD with a 400 CI 2BBL that got about 13 MPG.
The truck is pretty rusted on the bottom, but everything is still pretty strong. Maybe get rhino tuff or some similar thing and coat the rusty parts with it? And we got it from a guy in Columbus so it was northern Ohio.
I’ll try the ignition thing next time it happens, but I doubt it. I started it several times in a row and it still happened. But after sitting for half a day it was fine.
The filler neck is where the gas goes in right? I looked at that and it was a little corroded, so I’ll check it more closely. And I’m a teenager. I can’t afford it. Lol. I don’t use it too much right now because I don’t do too much driving.
Also on the passenger side of the tank I found a hose with a plug that wasn’t connected to anything. I followed it and it split to the rear tank also. But unless I misfollowed it(possible) it went to the battery? I looked, well more felt, the tank, and couldn’t find anyplace it would go in. But it lined up with the hole in the tank where the pump should be.
As for the idle problem, it wasn’t the control vale that was replaced. It was the control for a air pump?(something like that). But if I unplug it, the high idle stops, and my dad said it was fine to do that.
"The truck is pretty rusted on the bottom, but everything is still pretty strong. Maybe get rhino tuff or some similar thing and coat the rusty parts with it? "
As the old song told us, “rust never sleeps”.
No matter what you coat it with, the rust will continue to degrade the metal once it has begun its attack.
And, if you cover it up, you won’t be able to inspect those rusted areas in order to determine how far the damage has advanced in a few months.
Don’t cover up the rust.
ok new problem. muffler and exhaust pipes were pretty rusted. i saw were, because this evening the muffler decided to fall off the front pipes, and get jammed against the road. i jacked the tire up, and finally got the muffler unstuck. however, i also beat the living cr*p out of it, and i dont think it would be worth something as scrap metal(although neither would the truck!). would it be a good idea to get a new muffler and exhaust pipes off an old truck at the junkyard? i know one that has a decent system in it, like no rust that i could see, so should i just leave it?