Just purchased a 1991 F150 XLT Lariat 4.9L E4OD bone stock as far as I can tell.

Question: What are tho pros and cons to EFI?

 

Pros:
It is already efi

Better cold weather manners
better mpg

better power

dont have to spend the money to convert to carb since i think the 300 has a different head/intake bolt pattern, different ignition system, fuel supply system.

Cons:
will lose circuitry if there is a EMP attack

capacitors go bad and ecm needs replaced

cant run leaded fuel without hurt o2 sensor

cant adjust for e85 without a tunable ecm

 

All good points. Hopefully we avoid an EMP attack..

 

Outside of some very limited circumstances, there is no place where a Carburetor is preferable to Electronic Fuel Injection.

There are plenty of folks here that would like to argue otherwise, but they're wrong. Period.

Is the Ford EEC-IV system the most user-friendly EFI system in the world? No.
Is it the most tunable system in the world, and easy to make modifications to the engine with the stock computer? No.

But within the parameters the stock computers were designed for, it works fine, and just as well as any other fuel injection system of it's time.

If your truck runs, with the stock EFI, but is having some issues, invest in the code reader, pull the codes, and fix it. Pulling even a partially working EFI system, and replacing it with a carburetor is just stupid.

If you'd bought the truck, and it was missing the intake manifold, and somebody had hacked up the wiring harness, and there were no fuel pumps? Sure, I might be able to make the argument for tossing a Carburetor on it, for use as a yard truck or something, but that's about the *only* sort of circumstance I would do so, with an OBS that came from the Factory with EFI.

 

No way I would convert an EFI vehicle to a carburetor anymore than I would convert my carbureted vehicles to EFI. The other obstacle is that the E4OD is computer controlled so you would either have to replace it with a different transmission or get a stand alone computer system for it.

 

This is the input I’m looking for.. Thanks for your time!

 

Didn’t even consider this. I’m a new owner and figuring things out slowly. Replies like yours are invaluable!

 

There are more cons related to the engine type in your truck and the vehicles age than whether it is EFI or carbed.
The I6 is the only engine Ford used that has the intake and exhaust on the same side of the cylinder head, this severly compromises it's performance potential and creates problems none of the other engines suffer from like fuel system overheating. Despite that there are plenty of fans of this motor based on how easily it seems to be able to push a vehicle around, you just have to be content with the amount of power delivered in stock form because there isn't a lot more that can be be easily gained.. at least relative to the V8 engines which have a fair bit of untapped potential and also have hugh aftermarket support.
The vehicles age is the other thing that is a significant con that directly relates to the EFI system, wiring is a major component of any EFI system of course and it deteriorates badly in some cases after 30+ years in the hostile environment under the hood of a vehicle. The good news is the EFI in your truck is pretty much a stand alone contained system that only controls the engine and trans... it's not integrated with other system like newer vehicles, so if you had to change out a wiring harness it could be done.. the only problem would be finding one in good shape.