I’ve got a ’98 1500 with the 5.9, automatic, 4X4, 80,000 mi. and original catalytic converter. I'd like to get some advice on replacing the cat on it (do I need to?).

First, the O2 sensor after the cat threw a CEL code [>:] (guy at Autozone checked code for me). Did a little research on the forum about a bad cat causing the downstream O2 sensor to set off the CEL. The advice on that was to check the temperature of the exhaust pipes going into the cat, compared to the temperature of the pipe coming out. If I recollect, the outlet should be about 50 degrees hotter than the inlet. This would make sense, as it indicates that the unburned fuel is being eliminated (burned) and causing a higher outlet temperature.

I got a hold of a temp gun at work and did a little test here at home. I had the missus increase the rpm to about 2300. I then used the temp gun and shot it at each cat inlet pipe. Although the temps were jumping around, they half-assed stabilized at about 450 degrees for one and at about 550 degrees for the other.

Here is where it gets interesting…when I used the temp gun on the outlet, it showed about 270 degrees. This seems like a pretty radical drop in temperature. I would have assumed the temp should have gone up.

Can I assume from this that the cat converter has crapped out on me, and that the downstream O2 sensor is correct?

If so, it looks like I may be in the market for a new converter (I don’t believe 1998’s with the 5.9 were included in the “catalytic converter warranty extension”. Am I right?

Thanks in advance for your help.

 

The temperature should go up a few hundred degrees between the inlet & outlet if the converter is operating efficiently.

The 98s are covered in the catalytic converter replacement deal. 96-01 are covered.

Do you have an air pump under the hood as well?

 

Rom,

No, I don't have an air pump - at least not belt driven.

Seeing as how my outlet temp was about half of the inlet, do you think it is the cat?

If the cat might be covered under the warranty extension, maybe I should let the dealer take a peek at it?

Let me know what you think. By the way, anybody got a link to the "warranty extension" handy?

Thanks!

 

Yup, I'd let the dealer look at it/replace it.

Here's the link to the warranty info: https://dodgeforum.com/m_352822/tm.htm