hi all i have been working on this truck for a while now and am almost done. I have 3 questions.
1. I was wondering for the tale gate (mine is rusted beyond repair) is the tale gate this truck year specific or like the carburetor in this truck was the same model used for a few years?
2. my engine head gasket is leaking a little - medium. how essential is it I replace it and if I replace the head gasket should I replace the carburetor gaskets and the exhaust gasket as well (is there any other gaskets I should replace).
3. this truck is carbureted but has a o2 sensor (stock) I was under the impression that carbureted vehicles dont have 02 sensors, would a faulty 02 sensor cause my gas mileage to be 9mpg in city? my dad (previous owner) said he managed to get 12mpg in city (5 years ago).

thanks

 

You should be able to swap out tail gates with model years that use the same body style. If your head gasket is leaking you should probably replace it. You don't want coolant in your crank case and you don't want engine oil in your cooling system. Loss of compression and overheating could become issues as well and it will most likely at some point result in a break down and probably at the most inoportune time. When you replace the head gasket you can probably leave the carb on the intake and remove it as a unit. You should replace gaskets on everything you seperate during repair. The O2 sensor supplies your computer with a signal which indicates either a rich or lean condition during engine operation. This would effect mileage but it sounds your mileage issues maybe more a combination of things rather than the sensor alone

 

yeah if your getting collant into your oil system (you shouldn't get oil in you coolant because the collant system pressur is higher than oil pressure until you lose all your coolant than it works backwards, not good) that might decress your mialage. Replacing the head gasket will be pretty easy with the strait 6. I would say leave the intake and exsaust manifolds if you can so that you don't have to buy new gaskets but if you do take them off just replace them. But yes a bad o2 sensor will also decrease you mileage and are you sure it's carborated and not throttle body because ford started doing fuel injection in 85 because an o2 sencor wouldn't have much purpose on a carb

 

it looks like it is carburated to me, the air filter sits right on top of it, I will try and get pics tomorow at school. I went to napa online and searched the carburetor they show it as being a carburetor.

is there any way to tell if it is throttle body or carburated (I am realy new to all this, it is my first vehicle and every thing i have done on it has been my first)

 

yeah my 93 dakotas the same way it kinda looks like a carb but it's throtle body. If there's wires running to it it's most likely throttle body. But yeah if you get a pic we'll be able to tell right away. But I thinks it throttle body

 

First off, you DO NOT have throttle body fuel injection; you have a CARBURETED system. And YES, your truck uses an O2 sensor to adjust the air/fuel mixture at the carburetor, and if that sensor is bad, it WILL affect gas mileage.

In 1984 - 1985, Ford used a "feedback carburetor" on the I-6 and some V-8 models. A feedback carburetor is sort of a cross-breed between conventional mechanical carburetion and electronic fuel injection. An electronic carburetor, if you will. This system uses an EEC-IV computer that controls air/fuel mixture at the carburetor, engine timing, and all emission functions. Because all these functions are controlled by the computer and not mechanically, you have to make SURE they are all present and the sensors are in working order, or else the truck will not run as it should.

Looking under your hood, you will notice a throttle position sensor at the carburetor, map sensor, O2 sensor, wires running to the distributor, and a whole mess of wires running into the firewall that goes to the computer located under your dashboard on the driver's side. All of these components are what your truck needs in order to run correctly.

On these models, you can't just start unplugging stuff and removing emissions equipment without affecting the operation of the entire vehicle and that includes gas mileage and engine power. For example, if you replace the feedback carburetor with a conventional carburetor, the computer cannot "read" what the carb is doing and therefore it cannot adjust the air fuel mixture, which in turn will effect engine timing and emissions components. The result would be bad gas mileage and poor power and performance.

 

Great post Lariat 85.

 

Very concise, Lariat 85. Your input is appreciated.

May I add one other possibility regarding poor mileage? There is a sensor located on the thermostat housing. On my son's 1984 stock 4.9L with feedback system, this sensor went bad and immediately, the exhaust was extremely rich and highway mileage [on a trip at the time] dropped from 20+ to 12 mpg [yuck!].

Upon replacing the sensor [fortunately, rather inexpensive and readily available at parts stores] the previous good mileage returned.

 

I dont want to replace the carburetor, i just want to find out whats wrong with the mpg, am i able to just replace the o2 sensor with the proper replacement one? also should i replace the MAP sensor and the Air Charge Temp Sensor?

1986F150six was the sensor you replaced the Air Charge Temp Sensor?

 

hears the pics

this is the air intake the 2 hoses on the top are attached to my air charge temp sensor (is the connection right?)


hears the air charge temp sensor from bellow.


hears my carburetor


hears a side view of the carburetor (passenger side to divers side)


there's the 02 sensor


also should i replace the EGR valve? will that affect the fuel efficiency?
I have replaced the spark plug wires and the pcv valve thinking those were the problems about 3 weeks ago but they haven't changed anything.

 

Any emissions components which are defective could effect mileage and driveability as they are all integral features of the EEC system. A poorly functioning carb or defective feedback solenoid would brutalize your MPG's all by themselves.

 

kjay is absolutely correct.

What sensor was on your thermostat housing, Six? My '85 Lariat had a thermal switch there that I think controlled the EGR valve my truck used to have. Unfortunately, my truck was hacked up when I got it; some emsissions equipment missing or unhooked, wrong carburetor, loose vacuum hoses, etc. and it was a headache to figure out with the feedback carburetor system; typical of old trucks of this vintage. Thanks to this forum, I managed to figure it all out and I now have a good, reliable ride.

The EGR and all those other sensors aside from the air cleaner sensor may effect fuel efficiency if they are bad. There should be a code reader (red plug-in) somewhere on that truck that you can pull codes from to tell you if those sensors are working correctly, but it is going to be difficult to find someone who knows how to read codes from a truck this old.

When in doubt, it is always a good idea to replace the spark plugs, plug wires, and the PVC valve. YES, the O2 sensor should be changed periodically as well. Any auto parts store should carry it. If the O2 sensor is bad, it could very well be causing your problem.

From the engine pictures, it looks like Mattthegreat has a nice, original, unmolested truck there! I see the original carburetor tag still on it and the hot air choke is still hooked up. You just don't see very many orignal trucks like that anymore. Your a lucky man to have an engine that is not all hacked up.

Thanks, Chief. Remember, when a member helps you out and you feel so inclined, you can click on the little heart to the far right of their name and leave them "rep points." Those are the red squares that add (or subtract, if you hit the - symbol) from a person's reputation around here.

 

thanks for the help lariat 85 I will replace the spark plugs and o2 sensor when I next am in shop (Monday) my dad (previous owner) used to have a mechanic who could read the codes but be retired and moved there is no one in 100km that is able to read codes from old vehicles, I have no interest in traveling a 200km round trip just to find I need to replace a 50$ part, it would cost me that much in gas to begin with.

I am still wondering about the air charge temp sensor, on napa online they show the part but they also show a connector for it (wires and a plug, I only have the 2 hoses coming off of it, is that supposed to be like that?

http://www.napaonline.com/Search/Res...99&Ntk=Keyword

the top 2 parts are what I am looking at.

 

Quote:

Originally Posted by kjay

You should be able to swap out tail gates with model years that use the same body style.

Be aware that 1980 & 1981 use different latching & support mechanisms; if you
get a tailgate of those years, you will have to switch around and possibly
fabricate some components to make it all work right.

 

This is 100% true. Mine has most of the feedback system missing, rotted or just plain broken and I average 9 mpg at best with a 300 6cyl. I plan on doing a Duraspark distributor swap and replace the tired, worn out 1 barrel carb. Been playing with the idea of swapping in an, '85 HO 5.0 and T5 I have in a rotted down Mustang GT. Motor and trans are still in good shape.