Rebuilt 4.0 with automatic seems sluggish, can't go on highway without the slightest hill causing the auto to downshift and it's a dog. Short block done by reputable engine shop, I did heads, cam, timing chain basically all of top end. Truck fired right up after rebuild, I have at least 15 K on it from rebuild but the more I drive it the more it seems to me it is off. Truck has passed emissions no problem, idles and runs smooth but lacks power. When I did it, new cat, and exhaust. Tires are just a hare bigger than stock, maybe 29-30" and has 3.73 gears. Its 4x4 extended cab auto. The only real ? in the thing is that dam cam sensor which is a bear to get at. I had the cab off when I put a new one in the new engine, I followed the install procedure but on the 4.0 you don't set it with the little plastic cap tool, you set it to a value on a meter. Now the truck starts and runs OK, but is it possible to have the timing off enough for it to lack power yet still start and run smooth. Don't know how I will get to that to reset it, I see videos of guys doing them but mostly 3.0's in chassis. Really no room behind that 4.0 and firewall. Also I forgot , on rebuild all new fuel injectors also. Would a Dealers scope pick up on the cam sensor or timing issue? I'm 55, in my days we had a timing light and rocked the "DISTRIBUTOR" to set timing. LOL

 

I am 63 and don't miss the 'bad ol' days at all lol.
Still tuning carbs and setting distributor timing, but when I want to not when I HAVE TO

You should get a P1309 code if Cam sensor is not timed correctly
P1309 Misfire Detection Monitor not enabled <<< thats the Cam sensor out of time with Crank sensor
The Crank sensor is the main timing sensor, computer uses it to time spark and injectors
Cam sensor spins at half the speed of crankshaft sensor so has more "resolution" and can be used to time injectors better, i.e. spray fuel just when an intake valve opens

It would be possible to have it 180deg off, and maybe not trigger P1309, and it could be a bit gutless, but a long shot

Good read here on setting 4.0l Cam sensor: https://therangerstation.com/tech_li...hronizer.shtml


I would test vacuum at idle, should be 18-21"

Are you using stock exhaust manifolds?
They are tuned for mid-rpm power, if you change them then you lose that power

Also check throttle cable, press gas pedal down to the floor and hold it down with a stick against the seat or a weight
Then go to engine end of cable and see if you can open throttle more
If so Google; Ranger throttle cable mod
Very easy fix

 

es, it has the stock exhaust manifolds, Throttle cable when matted opens butterfly fully, will try vacuum guage this week, where is a good place to tap in?

 

Usually there is a vacuum manifold on upper intake with a capped port or two, power brake vacuum hose or PCV hose usually connects there