2005 ranger...loss of power?

Some wires and plugs fail under load, but pass in the shop when idling or being revved. This is not a load test. You would be advise to take it back and ask him to drive it for you so he might witness the 'under load' condition.

Question: Do you ever hear a ticking noise from the engine when you start up the vehicle?

If you do here this noise and it tends to stop after a short while, it could be the hydraulic valve lifters are sticking and not opening the valves either partially or fully. This due to gum residue from the oil. In that case add a bottle of SeaFoam or B12 to the engine oil and run around for a week or two then change the oil. You will then see a vast improvement as the Seafoam or B12 cleans out the gum from the internal parts of the engine. Also, add a bottle of SeaFoam or B12 to the gas tank. This will clean the injectors and keep the inlet valves clean.

mmalky: 50 years diagnosing and fixing large and small lawnmower engines.

The loss of power could be a few simple things, the fuel delivery system may not be functioning right at this time. The possibility is air flow, fuel pressure, oil pressure, spark, or exhaust restriction. If you have already checked a few of the items your list gets shorter, the fuel delivery may be suspect for my first thought. Is there an odor of gas around the fuel tank area, the rangers trucks are notorious for sending unit leaks. The unit may have developed enough rust to cause a hole which will decrease the efficiency of the fuel system, result is loss of power due to lack of gas flow. The ecm module in the ignition system may be a culprit as well if it is out of range it will not send the right spark load. The last thing is the exhaust system if it is too clogged, this will choke out your engine due to over restriction, good luck

In general, motor problems, such as a blown head gasket or warped head.

Catalytic Converter maybe? Unscrew the o2 sensors out before the cat and drive it. Will let you know real quick if that's whats wrong.