2001 F250 v10 with 79K miles.

Lots of pinging under load. Cleaned MAF, replaced fuel filter, air filter, and EGR. Read the other day a clogged cat can have that effect since the truck isn't "breathing" right. Loss of power and ping.

Today I used a FLIR thermal imaging camera (thanks to the FD) and measured the temp at the front of the cat at 405. The back of the cat was about 400 or a little less. My understanding is that the back of the cat should be significantly higher in temp than the front. If that's true would this be indicating a clogged catalytic converter?

Your thoughts are appreciated!

 

See if there are any codes, as I think a clogged cat will throw a code. Should actually trigger the cel too though.

 

The CEL is not on.

 

There is no code that says you have a clogged cat. There's a code that says the cat isn't working, but that's it.

 

Would those codes be related to the O2 sensors not working properly?

 

The O2 sensors are tested for proper operation before they are used to test the performance of the converter. While the testing is never perfect, the test routine does a pretty good job of sorting things out.

Check out the relevant OBDII manual for the details. It lists the prerequisites for each of the monitors.

 

It's not throwing any codes. I don't notice any type of miss or anything similar. Just the pinging under load and a lack of power.

 

One of the most frustrating things about even the most technical people when it comes to the V10: Is there an O2 sensor after the cat? If not, the truck is OBD-I not OBD-II and will never throw a code for the catalytic converter

Nor a code for a lot of other things that you would expect it to.

That 5 degree difference in the cat temps does seem to be off, theoretically. You could disconnect the cat at the three-bolt flange and drive it and see if that helps. It'll be loud, but oh well

There are also back-pressure testers that can thread into the O2 sensor bung to tell you how much pressure is building up. That might be a good thing, if you can find a rental (or free rental) at a local auto parts store.

 

That could be caused by any number of things.
If the engine were just sitting there idling and the converters hadn't lit off, those readings are completely normal. We don't know if you performed the test properly.

 

There's an exhaust back pressure test kit on ebay for $20.
It's basically a low pressure test gauge with adapters for the O2 port.

 

Correct.....should have described it as something’s wrong with the cat. Had it happen on a 2013 Taurus last fall; they were about 80% clogged I think

codes at least point you in the right direction

 

A mechanic's vacuum gauge (that's what it kinda looks like) connected to intake manifold will sniff out any exhaust restriction in a few seconds, along with a couple dozen other engine derangements. Very old school, aka "Steampunk Scangauge".

 

I ordered a pressure tester from Amazon and will run additional tests this weekend to confirm if my temp test was accurate. Need to confirm the cat is bad before throwing money at it. (Those things are not cheap!).

I'll update this post with the results of the pressure test.

 

The good thing is, without an O2 sensor after the cat, you could just cut it out, and with two of these and a piece of straight stainless pipe, do without it while you figure out what to do... Of course, it depends on what state you're in, and if you need it for emissions testing. I do not advocate removing cats just for the heck of it - but it's OK for short-term testing or until you get the money for a new one

 

I removed my four bad cats and only slightly regret it.

1. CEL forever. Though I’ve heard you can fool the ecu by partially covering the o2 sensors... haven’t tried it though.
2. Stank pipe! Don’t stand near the tailpipe when it’s running. It’ll wilt flowers for 20 yards. Also embarrassing if you have a customer near enough to smell it.