Just curious. I am anxiously awaiting Friday to fill up my tank and see where my MPG is after a new map, tps, thermostat, and o2 sensor ... if it's still terrible I might consider at least start daydreaming about going EFI on my 84.

 

As far as I'm aware the 300 I6 was never port injected or CFI but went from feed back carb to multi port injection.
Ford's CFI (central fuel injection) systems were not great, Unlike GM who's port injection (CFI) systems were quite good. So Ford just made the jump to multi port injection from feed back carbs on most engines.

 

Were the CFI (throttle-body fuel injection) systems any better than the Ford feedback carburetor system?

 

In short no.

Just as complicated (more so maybe even) less reliable, non standard fuel system parts that are now basically all obsolete and not supported by the after market (Mind you some of the bits are excellent for carb applications) The throttle body's were to prone to failure they never operated right in cold weather fuel mileage was no better than carb applications the list goes on and on. This is why it is was so short lived Feed back carbs on Ford engines out lived Fords CFI

The only positive thing is they has sweet fuel line fittings and what not.

 

Interesting. Why couldn't Ford get the throttle body to operate right in cold weather? Did GM have this same problem?

 

Ford did theirs on the cheap they basically used the base of the VV carb they even had a choke cap dash pot etc and added the CFI on top of the base plate it was sort of like a feed back carb but with injectors rather than the boosters it was a real cluster of a design. GM did a clean sheet design for their TBI and did not try to rehash existing parts to work like Ford did with CFI.
So ya the Ford CFI used a choke for cold weather operation....... you can already see where this is going to go...... it was a total fail. GM on the other hand used enrichment and IAS to control idle speed. not a FN mech choke cap .

. It has been 30 years since I played with them but quickly came to the conclusion back in the day the best place for Fords V8 CFI system was right in the garbage they never worked right from day one and only lasted but a couple years. It was so bad Ford hung on to feed back carbs up into the 90's rather than fit their CFI . GM on the other hand abandoned carbs with zest in favour of their TBI
If you want a CFI system I would look stand alone or adapt a GM TBI system.

 

If everything is working, your 1984 with the feedback system can produce quite good gas mileage! What is "terrible" gas mileage?

 

That's the "right on" man.

In fact, the 1984 "feedback" carburetor actually got better fuel mileage and burned cleaner than the first few years of EFI on the 4.9! How does 23 MPG sound?

 

I calculated 10.3mpg on my last tank. Which isn't going to work for me!

I actually like the idea of the tunable carb, and would like to make it work, but I also need a functional truck. I had no idea such a thing existed before I bought this truck about a month ago.

The current daydream, depending on how the mileage is, would be to find an appropriate GM throttle body injection setup, machine an adapter, and build the electronics/software to make it work. Crazy as it sounds, this is more within my skillset (cnc machining, circuit board design, and programming) than changing a valve cover gasket and not having it leak afterwards...

I most recently changed o2 sensor and (temporarily) disabled the choke open right before filling up. My very next step if it's bad is to monitor the o2 sensor and see what it thinks is happening.

 

So your truck is running a feed back system? If so is everything working like the factory had it? If not then that could be why the 10MPG>

Also how are you going to 'monitor the o2 sensor and see what it thinks is happening"? I would like to know.
Dave ----

 

It is an 84 with the EEC-IV with feedback carb, as I understand it. I've fixed all the codes, so I think I can say "yes" that it's working like factory -- as of when I last filled the tank, last week. My mpg timeline

Simplified timeline:

1. Purchased truck
2. Initial check: 17.7mpg, code for MAP sensor & TPS sensor
3. Replaced map sensor & TPS sensro
4. Then got 11mpg, and o2 sensor code about always lean
5. 10.7mpg for the next tank (still running w/ an o2 sensor code)
6. replaced o2 sensor and filled up (removed sensor was bosch and said "germany" not "w. germany" so it must have been replaced after 1990? New sensor is denso $12 universal one wire)
7. currently running on that fill up until tomorrow when i revisit pump #3 @ my local Jacksons

Regarding monitoring the sensor, I've checked its operation in the driveway once up to temp with a voltmeter. I'll either splice in under the hood or near the ECU and monitor with a voltmeter in the cab. I also kinda want to get some fun gauges, so maybe one of these:
I also might build an Arduino-based data logger to record some data over time as I drive. Maybe throttle position, rpm, o2, and maybe MAP ... and then i'm halfway to building my own ecu....





(from: https://sites.google.com/site/chrish...reference_page)

 

Aren't "port injection" and "multi-port injection" the same thing" "Port injection is injecting the fuel right at the intake port. As long as you have more than one cylinder you have multiple ports.

 

If the computer system thinks the engine is running lean, then it's going to try and make it richer by turning up the fuel. It only knows what it's told, so if the O2 sensor is lying, then it will get terrible mileage. I think I would disconnect the O2 sensor and see what code you get then.

 

The o2 sensor was definitely bad. There's a new one now that tests good (in the sense that it goes up and down if I fool with the mixture manually) ... hopefully my mileage will be much better, when I check it tomorrow. It was interesting that the mileage got *worse* when I replaced the MAP sensor... i suspect it was in some kind of limp mode, as it had very little power (no spark advance is what it felt like) .. with the map sensor then working, it started to trust the o2 sensor, which was always reporting lean... so it ran rich.

The other wildcard was the choke, which is now disabled, but might have been stuck closed at various points.

 

If the choke sticks, you should get a "too rich" code from the computer. It will then try to lean it out all it can, and when the O2 says it's still rich from the choke being stuck, the computer will give up and throw the code.