Holy Fugged plug Batman!

 

Plenum gasket is blown I bet. You didn't change or look at the plugs when you put in the new cat did you? Check the plenum and replace if needed. After that run tons of techron through it, you may get lucky and just have some major carbon build up on the valves.

http://dodgeram.info/tsb/2000/09-05-00.htm

 

Ouch!

 

I replaced the plugs and wires about 2 months after I replaced the cat. Like I said all the plugs except #8 looked great. I'm almost positive it's pinging. The durango in this video is making the same noise around the 3:45 mark.
http://www.youtube.com/watch?v=JuY3CICc70Q
I'll check the plenum again tonight. So a bad plenum can cause pinging? What else could cause it? I know my spark plugs aren't routed right according to the tsp. Could that be the reason?

 

The plenum indirectly can cause the pinging because of all the carbon build up from the oil. Then when the cat went bad that is the first cylinder to take all the extra heat. If the plenum gasket is ok , then you might have the infamous cracked head at the valve seat. Or it could simply be a bad injector as previously stated. And since you replaced the plugs 2 months after, the plug was probably no good 2 months prior. Which in turn contributed to the death of the cat. Whether it be the plenum or the injector.

 

zman17, I'm a little confused by your post. How would a bad plug kill the cat? Wouldn't the bad cat kill the plug (because of the excessive heat)?

So you think I either have dirty injectors because of a blown plenum, or a cracked head. Are there any good/easy ways to test the injectors? Is there a better way to check the plenum than just looking for pooled oil in the intake?

I've been running 89 octane gas for a couple tanks so most of the 87 should be gone, and today I noticed that I couldn't get it to ping hardly at all. I only heard one little ping when I took off from a stop sign. So I'm thinking that the higher octane gas helped a lot. Tomorrow I'm gonna buy a full tank of 91 octane to see if it helps some more. What does it mean when there is less pinging with higher octane gas? Friday I'm gonna pull and inspect the plugs, and thoroughly check the plenum gasket. I'll report back with what I find. Thanks again.

 

Are you running a programmer with advanced timing? 87 octane and advanced timing = ping

 

I worded that wrong , and no you don't have dirty injectors because of a blown plenum or cracked head. Faulty injector , cracked head , or bad plenum gasket will slowly destroy the cat . Here's how to check the plenum, http://dodgeram.info/tsb/2000/09-05-00.htm

 

The ignition is all stock. Autolite 3923 plugs with mopar wires, cap, and rotor. Thanks zman, I'll check that stuff out friday.

 

I still don't see any oil pooled in the intake, but I think the plenum is the problem. I started my truck with the remote the other day and I noticed that it was burning quite a bit of oil for the first few seconds, and then the exhaust looked normal. I was 1.5 quarts low on oil the last time I checked, it hadn't been that long since I topped it off the last time. The pinging only stops with 93 octane gas. I'm gonna start looking at replacing the plenum.