Which transmission do you have?
In this thread you say it won’t go into overdrive, on the other ‘more power’ thread you say it has a three on the tree.
sorta its a automatic with drive 2, 1 gears its made for highway ive been told by my father
i cant trade it in for something newer this was my great grandfathers truck right off the dealers lot so thats not an option
Three on the tree is a 3-speed manual transmission with the shifter on the steering column.
yes i ten corrected that commement by saying it is a automatic with three gears
That statement makes me think that it should be kept as it is. I would do a minor restoration such as a first class detail and have the thing look really decent with a few repairs if necessary.
Common reasons for diminished engine power
- low compression
- ignition timing advance not working
- egr system activating when it shouldn’t
- fuel mixture problem (vacuum leak, pcv valve, injector problem, O2 sensor, MAP, TPS, CTS, etc)
- brakes partially on all the time
- transmission problems can sometimes mimic engine power problems
I keep older vehicles myself but this is likely before the days of scan tools and OBD systems of any complexity. Are there any kinds of diagnostic lights? I would give it a good tune-up if that hasn’t been done in a while. I am sure it will be cheap and easy on something this old. Distributor cap/rotor, plug wires, plugs, and even ignition coil are in order. You might hold out to do the ignition coil until the last as those are usually the last to fail. They should be cheap for this thing though.
When were the vacuum lines last replaced? You can try spraying carb cleaner around under the hood near the vacuum lines with the engine running. If the idle changes you found the problem. These lines are cheap so I usually just find out the sizes I need and buy a few feet of each. I cut them to length and swap them out one at a time so I don’t get confused. The old ones get tossed in the trash can outside the parts store along with all the old windshield wipers sticking out like arrows.
Is the thermostat stuck open? YOu might open the radiator cap with the engine COLD ONLY and start the truck. Is the coolant moving right off the bat or not? If you see active circulation it is likely stuck open. This is better than sticking closed but will kill your mileage.
Have you checked engine compression? Maybe the engine burned a valve and that cylinder would have very low to no compression. That would hurt gas mileage and cause rough running, especially at idle. This would also be much more expensive to repair than any of the other issues I mentioned.
Did this truck have a lockup torque converter? Again, this is a tad before my time. The other suggestions about the timing advance are also something you need to check on.