So I recently fixed an issue with a bad MAF. The truck (05 5.4l) was running with +50% fuel trims on both banks, for probably a year. I don't think it was actually running lean, it was just dumping fuel in because of the MAF. Replaced the MAF and trims are pretty good now but I think the cats got clogged, here's why I think they are:
Hesitation/slight bog on hills or acceleration.
The voltage oscillation on sensor #2 both banks is the same as sensor #1. Shouldn't it be sitting close to .5v without much fluctuation?
Fluttery sound from exhaust
obd catalyst temps on both banks is 1300-1650 anytime im on the gas (2000rpm+)
no codes though.

Does it sound reasonable that they are clogged and need to be replaced?

 

You can take it to a muffler shop and have a backpressure test done.

 

Ok cool, I may do that if this deal falls through but I saw a local guy is selling new cats for $100 so I thought I might as well replace mine for that price. Only issue is that I have the 2 cats and these are 4 cats (early 2005 vs later models?) Would it be an issue replacing my 2 cat system with the 4 cat system?

 

2wd and 4wd use different cats. They should work if they fit and the O2 bungs are in the right place.

 

Well, that alone indicates the cats ain't converting. Should eventually get P0420/P0430 DTCs.

Useless "data". Ignore.

 

IMHO...avoid cheap cats... the oems are really very high quality. What I can suggest is before you go through the work of R&R the cats, try a bottle of rislone cat cleaner. I use this multiple times in our older vehicles especially prior to doing our biennial smog tests and I can say it definitely works cleaning out the cats!

 

Thanks for the suggestions. I also did a engine vacuum test and it was 19 in-hg at idle and dropped to like 14-15in-hg at a steady 2000rpm. That is indicative of clogged cats too right?

 

There are three ways to diagnose a faulty catalytic converter:

1. Vacuum Test

Before conducting this test, you’ll need a vacuum gauge.
Follow these steps to conduct a vacuum test:

• Set the car to neutral or park.
• Connect the vacuum gauge to a direct vacuum line, like the direct intake manifold.
• Start up the car and allow it to idle until it reaches prime operating temperature.
• The vacuum gauge should return a reading of 18-22 Hg.
• Start accelerating and allow the car to reach around 2500-3000 rpm.
• The vacuum gauge reading should reduce before returning to the previous level. If it takes a long time to reduce, you likely have a bad catalytic converter.

2. Temperature Test

To perform a temperature test, you’ll need any type of thermometer, like an infrared or kitchen thermometer.

• Start your vehicle and allow it to reach optimal operating temperature. Take it for a short drive to let this happen.
• Set your vehicle to park or neutral.
• Measure the temperature at the inlet pipe that connects to the front of the catalytic converter. Repeat for the outlet pipe, which connects to the rear of the converter.
• If the front temperature is the same as the rear temperature, it means that there is an issue with the catalytic converter.

3. Back Pressure Test

For this test, you’ll need a back pressure gauge.

• Start by removing the front oxygen sensor and replacing it with the back pressure gauge.
• Start the car and note the reading of the back pressure gauge. A reading between 0-3 PSI is normal.
• If the reading is around 8 PSI, your catalytic converter is clogged.
• Reinstall the oxygen sensor.