Some one help me figure this out. I have a 2001 dodge ram 1500 318 nv3500 4x4 120,000 miles. I only get 10 to 12 mpg on the highway and have what seems like a loss of power and find myself downshifting for even small hills. The truck idles fine but around 1400 to 1600 Rpms sometimes will lose a little power and surge back slightly. Any pointers?

 

This belongs in the Tech Section....A mod can move it for you.

Probably plenum, cat, and O2 sensors...

Compression test first probably not a bad idea either....

 

A complete tune up with new plugs and distributor cap isn't a bad idea either. Running sea foam through it and cleaning the throttle body might help. Checking the air filter and air pressure in the tires would be easy to do

 

Get the catalytic converter pressure checked at a muffler shop. You're describing symptoms of a clogged cat.

 

You could also whack it with a rubber hammer and see if you hear any rattling.

Also can take out front O2 sensor and see if it drives any better

 

And it sounds like you IAC valve is trying to go south.

 

Idle should be 550rpm warm. Massive vacuum leak so I would check plenum, hoses, etc. When my cat went it never lost power, just rattled at stoplights.

 

Same here. A chunk of catalyst fell apart and bounced around.


Granted, my exhaust guy pounding on the exhaust pipe while installing my muffler didn't help either. But it gave me the reason to swap the cat out.