I have a 98 Ram 1500 V6 3.9
I have had the cat replaced with a high flow cat
I have changed the tranny filter and oil
no check engine light

When im driving it has decent power (for a V6) but when I get over 50+ and i get going on ANY type of up climb or little hill my truck starts to slow and losses power like crazy I'm not sure whats causing this any info that I can get will help out

 

Have you fixed the plenum?

 

I have not touched that yet... I keep hearing how the bottom plate warps or something like that and causes it to leak... Is this correct?

 

Yea and which in turn clogs your cat which will crack your head which will cost you more money than its worth and all of this causes your truck to have no power....

 

Read the plenum sticky on top of the forum.

 

I'm having the same problem on my 2000 1500 with the 5.2L. Runs good until going up a hill and then won't go over 35-40 mph. Engine does not seem to be missing or knocking on the hill. New Tranny, New plugs (plugs were about 4 years old and all were burning clean with no deposits) New Wires, Cap, and Rotor, 2 new O2 sensors. There is no difference in performance. Vehicle just passed emissions with no problem. I'm thinking maybe the MAP Sensor??? Would it have passed emissions if the MAP were bad?

 

If the map doesn't set a code, they apparently don't care.

Have you done your plenum yet? You have some of the signs of a blown one.... and possibly a clogging cat?

Take out the front O2 sensor, and go for a drive. Got more power? Cat is plugging up.

 

Thanks for the info. I will follow your advise starting with the 02 sensor.