Yes they are and my bad for mixing them up

Port injection should automatically imply multiport injection /MFI. A few manufacturers early on called their throttle body injection, port injection in the late/ mid eighties to try to hitch to the multi port wagon. but that was short lived.

Really I should have been more clear. Ford's throttle body system was called CFI ,Central Fuel Injection GM got it right by actually calling it what it was. TBI, Throttle Body Injection,

Mulitport Fuel Injection,MFI and Sequential Electronic Fuel injection,SEFI are both mulit port systems but are are not the same . on the surface they're same with each cylinder having it's own injector, but that is where the similarities end.

In MFI systems the injectors all spray their fuel at the same time or in groups, Ford paired the injectors much like in the first DIS coil packs. In SEFI systems each injector nozzle independently sprays fuel immediately before or as the intake valve opens. This is why Ford made sure to identify SEFI in their applications , to separate it from the less advanced MFI units GM was using at that time.

Fords CFI system was a bit of a bodge job initially unfortunately, it was designed in house and was integrated in house with the EEC and was a dismal failure. They should have gone to Motorola (the ones who developed the EEC system) to do the integration. The system just did not work well at all. It was well designed and over built in many aspects but the integration with EEC was poorly done as were most of the throttle bodies.

 

My son's truck is a 1984 with 4.9L and feedback system. There was a problem where the gas mileage suffered and the idle was too high, even with the idle speed screw backed out to where there was no contact. There was a vacuum leak, which caused a lean condition.

By the way, before gasohol, this truck would return 26+ mpg on the Interstate. It has the 4 speed manual OD and was "born" with 2.47 rear gears [now has 3.55]. It came with the tiny spoiler on the bottom of the front bumper.

 

So, filled up and calculated 13.4mpg better than 10 but quite a ways from 26!! Besides what I mentioned above, i need to pull the spark plugs, check compression, look at the rotor and cap, and check the timing. Vacuum seems "ok" but the needle does vibrate about 18 when idling.

Of course all my hard work flushing the cooling system has resulted in (presumably unclogging) a radiator leak.

 

Maybe this will help give you ideas for chasing any vacuum leaks: https://www.ford-trucks.com/forums/1...expensive.html

 

26 MPG is not going to happen.

Used to have a 92 Bronco, 4.9 EFI, E4OD, 3:55 gears and it would struggle to make 15 mpg and that was calculated with those big imperial gallons we used to use in Canada.

Now, I would be all in favour of fixing what you have rather than going this route, but FWIW, I know of a 300 six that was converted to GM TBI using pieces off a 305 SBC. It runs rather well, but still nowhere near 26 mpg.

 

15 would be fine, 18 even better!

 

https://www.ford-trucks.com/forums/1...-9l-300-a.html

 

Yep, I've read the whole thing! Not sure what's possible with my setup. Currently 65MPH is 2500RPM. My commute is 12 miles, with a quick on and off the interstate on both ends, which I think should be pretty ideal.

Battleplan as it stands now:

1. Check mpg friday (only thing i've changed since last tank is the oil, fuel filter, and pcv valve)
2. Check compression this weekend (and plugs, obviously)
3. Get set up to monitor o2 sensor, to see what it thinks is happening
4. Choke is disabled open, but I need to get it working for easier morning starts
5. Been keeping an eye out for an air dam, might 3d print some mounts and make something.

 

With your gearing [and tires?], the RPMs are much higher at any speed than my truck's. At 65 mph, the engine in my truck is @ ~1800 RPMs. An engine normally returns the best mpg at engine speed which approaches maximum torque, which is approximately 1650 RPMs on a stock 4.9L carbureted engine. Also, with the aerodynamics of a brick [our trucks], fuel mileage greatly decreases at speeds greater than 55 mph.

For Friday's drive, I suggest you check tire pressure and inflate to what was recommended for the truck, remove all unnecessary weight, shift into each higher gear as quickly as possible [short shift] without lugging the engine and limit your top speed to 55 mph. At 55 mph, the wind resistance will be much less and the engine RPMs should be ~2100. Pretend that there is an egg between your foot and the gas pedal.

Let us know how it turns out!

 

Friday will conclude a typical week of driving since i filled up. Also, I can't drive 55!! 65 is a requirement for me, so I need to find the best I can do at that speed. I've been driving fairly conservatively, otherwise.

Do overdrive transmissions have the final gear circled on the ****? Or is there some other easy way to id them in a junkyard?

 

I would like to know how you do both of them so when you get into them post up how.
Dave ----