Ram 1500 239 runs about 8 to 12 miles then backfires and looses power let sit a while and run good for acuople more miles before running bag again

General advice:After warming up track the problem:sparkplugs (even new can have the ceramic parts broken/cracked /wiring (after warming up the isolation get's soft,can loose spark power)/ignition coil(s) (gets hot,stop runnig),running reach,fuel pump/fuel pump relay.Best guess:fuel pump mallfunction (low pressure) related,fuel filter cloged/water in the fuel/fuel line cloged/chipped. Cheers,hope u figure it out,let the people know.

replace ignition coil

Has the exhaust ( catalytic converter) been check for proper flow? I would try a test pipe to by-pass converter and see if that helps. You used to be able to buy them, but a good exhaust shop can make one pretty quick, and then try it.

hi Jhlightcap.

The Common Problem: Rough Running Engine

A properly-operating engine should run smoothly and without excess noise. If your engine starts operating in a manner that gives you the perception of "running rough", it is likely due to a handful of common causes. A mechanic would investigate these common causes first in order to rule out a simple explanation for the engine's unsatisfactory operation.
The common causes for rough running in an engine are:

• Engine miss
• Vacuum leak
• Dirty fuel injectors
• Carburetor problems
• EGR valve
• Ignition coil
• Spark plug wires
• have a look at this link.

Rough Running Engine James on Engines 2

Repair your vehicle right away. Just click on the link I attached 1995 2000 Toyota Tacoma Service Repair Manual

possibly timing chain

fuel pump is a likely cause as it will run fine when cold and once it heats up it loses powers muffles backfires and dies.

you have a leaking intake mainifold gasket that is common on the model

the cat would have been supplying a certain amount of back pressure if everthing else check out fine ie compression put a cat back on

new fuel pump its in the gas tank