hey guys,

I have a project truck that I recently inherited. Its a 1987 F-150 Lariat Custom. It has the 302 engine with 4 speed (granny gear) transmission. My grandpa bought the truck new and put about 200,000 miles on it. Its a decent running truck, but has a couple issues. We rebuilt the motor a couple years ago. .0030 over bore, rv cam, just a small amount of work to pep it up. It has not ran right since. It has always run rich, excessively. I put a new computer in it, new injectors, took the cat out and cherry bombed the muffler (just a farm truck). The truck starts fine, but it doesnt idle well, it surges; hot or cold. Truck gets about 6mpg, grandpa said it used to get about 12 or so. Runs so rich, hooking a trailer up will be a struggle because of the exhaust burning your eyes. I am wanting to do some work on it for the sentimental value, and its in great shape. I plan on driving it in the winter and for hunting trips, so gas mileage is a little more important to me now then when we just used it on the farm. I plan on putting longtubes on it and all new exhaust since the old stuff is about worn out. More importantly, and the reason im posting on here is what to do about the stock EFI? I have thought about carbing it, but really enjoy fuel injection. Ive looked at the efi kits like fitech, just to replace all the things that could be issues, and this is the leading idea. But scrolling through pages on this forum, I have seen where some people rebuild the ecm and they are satisfied with that. What ideas or suggestions do yall have?

Thanks

 

First thing, you need to check for codes


If I were to guess, I would lean to 2 areas. Vacuum leak, and o2 sensors
Not sure if you inclued the o2 sensor back in line when you took the cats out, but you HAVE to have an o2 sensor for fuel managrment

 

Thanks for the reply. New O2 sensor when we put the motor back in. I have been thinking about a vacuum test, probably will do that when I get back home. Any suggestions or diagrams for that?

 

Run the truck at idle
Spray carb cleaner around where gaskets to intake as re. Plenum, lines, etc.
If engine rpm rises, you found the leak
Pay close attention to the metal juice c as n on the passenger inner fender

 

Pay close attention to the map sensor and it's vacuum source . Unplug the electrical connection at the sensor while running and see if it runs better.

 

Ok thanks! Is the stock computer able to compensate with the engine bore and different exhaust?

 

Yes. It only goes by information in from the sensors.

 

Hey guys. Finally had time to do as y’all said. Found a broken vacuum line and figured out they were not ran properly. (Couple of hundred my grandpa paid a shop to do wasted). I decided to redo the system with rubber lines. Fired the truck up and it stumbled at the beginning, but now runs smooth, idles steady at 1100 rpm. Still hesitated hitting the gas. Not sure of mileage increase yet. Didn’t have time to drive it much. Thanks for the suggestions.

I did order the pacesetter headers. Jegs is discontinueing the coated ones, so got those, should be delivered today. Just out of curiosity, what are people running pipe wise in these trucks? Dual? 2.5” or 3”?

 

If idle at 1100 you still have a major vacuum leak...….
I use dual 2.5

 

What should it be idling at? I redid the entire system with rubber hoses. Maybe a bad sensor then? I’ll drive it and pull codes to see if it’s sending anything.

 

Tried doing the paper clip trick to read the codes, the engine line just remains illuminated. No flashing or anything.

 

Try doing it like this
https://www.fordtruckzone.com/threads/how-to-check-codes-on-obd1-and-2-without-a-scanner.654744/

 

I’ll try it this way. Thanks!

 

Tried it that way, test light never lit up. Beginning to think a wire maybe cut or something.