Has the plenum plate under the intake manifold been repaired? If not, crawl on top of your engine (engine off) open the TB blades and take look into it with a flash light, if there's oil on the plate...Might be your problem.

 

Where are the other 4? How are we supposed to know what others said about it?
Here is a perfect example, I believe i asked this same question. Keep your thread post's together! If not link them.

 

1997 dodge ram 1500 5.9 magnum. I really need help diagnosing it, it's slowly losing power and I don't know why. New plugs and wires, would love to know the proper way to diagnose the distributor or cam sensor. Up steep hills has no power barely able to keep it going 45mph. Flat ground us alright but slow on acceleration and any small hill causes noticeable speed changes.

 

What plugs?

Sounds a lot like a clogged cat.

 

You can check for codes here, Also have the fuel pressure tested. Are you aware of the plenum gasket issue?

 

It was a clogged cat! Being stressed about my drive home from the holidays which is a 8hr drive with no power it finally came to me! I made a pit stop at a old shop I used to work at and they allowed me to use there tools to disassemble me exhaust. Shining a light inside my cat you could see the honeycomb completely collapsed and was pointed downwards rather then parallel with the flow. I've never had witnessed nor diagnosed a catalytic converter before so I was at a loss up until this point. I took a metal rod and hammer to it and now my truck has its ***** back.

 

1997 dodge ram 1500 with the 5.9 magnum. Just updating from my last posts for anyone else who may find this useful in the future. My issue started with a random miss fire code under heavy throttle and gradually threw the code more often. Within a span of a couple months my truck lost more and more power. I started with the basics plugs, wires with no fix. load tested battery and alternator output all was good. resistance tested ignition coil and fuel injectors all was in spec. bought a fuel pressure tester and fuel pressure also met spec. My next test would have been a compression test but kit was sent to the wrong store before the holidays. after a painful 8hr drive with the truck barely able to maintain 60mph on level ground I got to thinking more about what I was missing. Finally it clicked, being a new tech I had never had the pleasure of witnessing the diagnosis of a clogged cat but remember learning about some of the symptoms recently in a automotive school. loss of power and miss firing were a couple of them. And the fact that under heavy load is when the issue was the most obvious is what finally made it click. A hissing sound that changed with rpm I assumed was exhaust gasses escaping from joints from built up pressure from a clogged cat. disassembled my exhaust and shined a light to see my honeycomb inside my cat imploded and was restricting flow. Hammered it out the best I could with a long metal rod and truck was driving better than ever before. This took me much longer than it should ever had diagnosing this problem but I guess there is a first time for everything and I was unfamiliar with exhaust systems. Hope this helps someone and they don't stress as much as I did.

 

Merged all the misfires threads into one. Makes it easier for others to find, instead of having them scattered all over.