2001 1500 5.2L 169k miles

Seems to be a bit short on power. Going up a medium grade hill, it's having trouble holding 50-60mph. Pulling a 21' boat, it isn't able to get above 40-45mph.

Also, it's getting between 10-12 mpg which seems a bit worse than it should be.

I wasn't able to locate any vacuum leaks around the passenger side of the engine using throttle body cleaner.

Truck does have the wild vents issue, and I am going to install new check valves to fix that problem. Would this also be causing a loss in power?

Don't see any oil when looking down the valve body, so I don't think there's a plenum issue. Although by checking with a magnet, I do still have the steel plate installed.

I disconnected the upstream O2 sensor, and it does seem to have a bit more power, so not sure if the Cat is going bad, or if thats just extra power that I'd see from increasing that much flow in front of a functioning Cat.

I've been reading that a bad map sensor can cause loss of power, and other issues, so I'm going to check that next.
Update: Checked Map Sensor with a voltmeter, and it seems to be operating within spec. Plus I'm not getting any Map Sensor codes.

It has had a P1740 code for quite awhile, which is the a Torque Converter or O/D solenoid, however it generally seems to shift fine.

Any other ideas? Thanks.

 

You don't check for a plenum issue by looking down the throttle body.. Take it off and look at the veeeeerry back for any oil, it's not possible to back there with the tb still there.
And yes your cat is clogged

 

Physically remove the pre-cat O2 from the exhaust, and go for a drive. See if you have more power. Sounds like a failing cat to me.

 

Plenum, timing set, plugs, wires, cap/rotor, new O2 sensor, new cat.

CHOP CHOP.

 

I THOUGHT my plenum was ok even after inspecting the gasket on removal I was still not believing since it seemed intact I started blaming the PCV for the oil until I put it all back together and THEN changed the CAT and can now accelerate on hills again and went from 11 and change to 14 or better MPGs on the same roads. Full disclosure I also did a new cap and rotor in there at the same time.

 

Only blown plenums kill cats.

Well, almost only.

 

+1, the new cat will not last long. Also you need to replace the o2's.

 

I havent seen mention of this, is your plenum pan aluminum or steel? If its steel you might as well switch it for an aluminum pan and save yourself the trouble when it appears down the road.

 

curiosity can kill our cats as well

 

Curiousity can also burn us and our cats.

Just depends on what cat we're talking about.