Well guys, seeing the other topic here on i-6 efi vs carb, I decided the time was right to ask my Q's.

Just started computing gas mileage for my truck. It is a 1994, I-6 m50d with 2.73 rear-end gears and 129,xxx (forget what I am up to now). I treat it very nice and don't rev above 2000rpm with less than 1500 being normal. I bought the truck and drove it back from an hr and a half away from here. The truck had to have gotten around 19mpg. After that I had a tune-up done becuase things looked original, mechanic verified lots of stuff was indeed original!! So, new fuel filter, pcv valve, air filter, pcv breather, spark plugs (autolite copper), (heavy duty autolite wires), new rear end oil (lucas 80w-90).

Before I bought it sat for 6mo, but there was an oil change done 2 weeks before I got it because of the oil pan rotting, so he had the oil pan replaced. That is all I know except for oil at 3-4k and all other essential maint. done.

I'd like to think it should be getting better mileage now. Right now its at 13mpg, (I fill it every half tank, at 1/4 tank when its not winter,now its 7.5 gallons for 89ish miles was last fill up. Now figure in a bit extra fuel for warm-up during which i scrape the windshield in the winter, but it still should be better right? Although since i started checking mpg have been rising, (i don't fill up too often). It is mostly town driving about 40mi a week or sometimes 70 but its usually 70-90 in 2wks. (When it is really cold I will take it on a 20-40 min 65mph drive once or twice a week for engine and battery sake, so we will see then what highway miles are like.)

Last time checked, no codes. 5 days ago,although check engine light was on the other cold morning 2 days ago, (egr related) but when driving later in the morning it went off checked codes again and was fine???

So: what I am going to do: keep running injector cleaner in it a bit (mechanic told me to), get a definate code check one of these days with a buddy to help me, so I am not freezing my fingers off

 

The distributor hasn't been touched (probably is orginal because sparks were orig) because a screw broke (yes i did it stupid rust), mechanic says its rusted where it contacts metal on underside of dist., says don't worry about it unless in wet weather truck acts up. Is this okay or would it cause bad mpg? Should I replace ignition coil for mpg sake too?? Would they give me better mpg? Truck runs and start fine, takes a bit longer to start than v8s but told was normal, takes a bit longer in cold weather too, but hasn't acted like it wouldn't start, always cranks like it means it.

(The only other thing is that in neutral when engine is cold there is a delay in throttle response, you press the pedal and there is second pause before engine rpms go up, in only does this a few times even when cold and can't tell when driving and always seems to be fine when checked when warm???? It could be normal because I have seen other brands and cars do this too.

Thanks for your help!

I understand stuff can fail or go wrong w/out throwing codes so lead me in the right direction.
Conanski posted in the other thread: "If you are up to doing a little work we can help you get the most out of it." I have 2 weeks before I go home for Christmas break, what little time I have now (and I mean little I will give) and I should have more time in Jan. So be patient, will get my oil done this weekend hopefully. (Been about 3months, only use motocraft filter its whats on there now and what I always use, and valvoline oil)

P.S. All fluids are good, new tranny fluid, but do have a radiator leak, the thermostat seems to work and I always keep radiator and reservoir full. I will put a new one in probably in Jan. Sorry for the lentghy posts but now you have enough info, (it probably would have taken days to figure out all this stuff with the normal my mpg sucks help me post.

Later

 

If you got an EGR code it warrants look, even if the code went away. Any sensor problem will affect the operation of the motor, and a sticking/failing EGR valve could also cause the stumble you experience.

 

Yeah I will take a look. Seems plausible especially since I was at one time getting around 19mpg. How do you suggest starting to test it, the haynes manual has lots of stuff in it. Should I test the solenoid first?

Thanks for the help.

 

First look for a rusted/leaky EGR tube, and then look for cracked/broken vacuum lines, they get prety brittle on these old trucks. If all that's Ok then test the various EGR components. If you haven't seen it already this site has lost of good info on the Ford EFI system. www.fordfuelinjection.com

 

13 mpg around town in the cold doesn't sound too bad to me. I think that would be perfectly reasonable to expect if you had gotten 19mpg on the highway driving it home.

To give you an example, I recently bought a 92 f350 with a 460. It got 14.5 mpg driving it home on the highway (with a thermostat stuck open!) Now around town, with the short trips that I take it on, I'm down to about 10mpg, and that's after replacing the thermostat. I imagine it would have gotten closer to 16 with proper coolant temps on the highway.

My Lincoln LS can get 28 mpg on highway trips, but around town it only gets 18-21.

 

Driving the other day the tailpape came out of a fitting, the one after the cat egr etc to the main exhaust pipe came out.... I am thinking of what to do to fix it. Should it be welded? I think it was some type of heat shrink to fit on and just came out. (Exhaust flows pretty well out the shortened exhaust, truck sounds good too and has a bit more power I think it was the not having the rear support straps and now I rigged some in there and so maybe the twisting motion loosened the connection. Suggestions on fixing would be appreciated. (I don't have a welder so would take it to exhaust shop to be done if that is needed).


P.S. Checked EGR tube and looked good (rust wise), vacuum lines look good too. After get other exhaust problem fixed will check again and try taking valve out and cleaning.

Truck idles fine, 1000rpm for awhile, once warmed up drops to 700ish rpm. Truck starts fine in cold, takes a bit, but alway first try. From the miles I had driven thus far it has moved up to around 14mpg just looking at gauge and odometer.

 

Remove the EGR and clean it with seafaom. I've had to do this with my 5.0 every 30K or so.
These days, the auto world is just starting to realize the importance of cleaning the carbon off EGR related parts.

As far as fuel milage is concerned, your in Mn. The cold weather has caused the refineries to start suppling winter fuel. IE: Lotsa Ethenol blended into it. Expect a 3-8 MPG drop in fuel effeciency