94 Ranger with 4.0L fuel mileage down to 12.75mpg...

Ok, rather than play with oxygen sensor swapping around, I tried cheap ECM from a 91 Explorer with manual transmission as 91 and 92 only had single oxygen sensor and hey 50-50 chance the one it sees is not one that was throwing code on other ECM. Ok this one wanted to do the high idle thing, where the other one did great idle. Big hint maybe for anybody getting told over and over they have some hidden air leak. Maybe, but also can be ECM. But noticed even smoother running and no CEL getting mail and home.

I did fill tank last trip to town and 8mpg. But that was mix going clear back to before I found holes in the air intake tube. So took trip to cheap chinese tool store about 40 miles away and as mentioned started with full tank and accurate starting mileage. Stopped at gas station before coming home and topped tank. 15.83mpg!!!!! Now wasnt perfect, CEL did come on halfway there. But if anything ran bit smoother after that. And CEL didnt stay on when I restarted engine after going into store. But then reappeared when engine got hot again. One code complained about manifold pressure? Odd the 91 this is out of had MAF... Another that oxygen sensor reading lean. And third about something called VSS that wasnt used after 1992.

Main thing though was that i got nearly 16mpg. Twice mpg that I was getting. And about average for this engine from reading online. So its running darn close to best it can run.

I can live with that. A 4200 pound pickup, 16mpg is ok. Its what my 1960 Chevy Apache longbed with 235-6 (4.0L just wee bit bigger) and same transmission got. Though with long box it was more useful. It weighed bit less probably more like 3500 pound. Again the only reason my Ranger is so heavy is that its extended cab and came from factory as 4wd so still has the heavy front axle. In comparison a single cab short bed Ranger same year is little over 3000 pound. Carting around extra 1200 pound does make difference in mileage and performance. Though extra weight no doubt also makes it ride better. This Ranger maybe one of best riding pickups I ever owned.

As interesting as this little adventure into computer truck was, think in future if I need another vehicle this size, I use antique carburetor engine. So much less hair pulling frustration. I also so much prefer driving the 300-6 over pretty much anything. So put one in a modern body no more than 3500 pound, or if we have emission inspections by then, then find a solid antique that is exempt and put it in that. Easier to modernize brakes and steering, etc on antique than fight the computer. Can get away with it cause the 300-6 was first used in mid 60s before pollution controls.

Oh and this SM420 is one of noisiest transmissions ever, worse than the one in my old Apache pickup. Not bad in fourth, but it was growling up a storm going up steep hill in third, while trying to go 40mph. Thats another thing, way axle is geared and engine torque curve, third gear has to cover too much territory. Sometimes need a gear little lower and sometimes little higher where second and fourth are too big of a jump. So be kinda nice to have a 3a and 3b gear.... Now on those older straight sixes with max torque much lower rpm, they can get away with it.