My cel came on, P0420. This was a month ago. I know my cat needs changing and plan on doing this in the next few weeks. I'm driving on the highway go to put the cruise control and notice no cel. This was 3 days ago. Hooked up the computer and no codes. I did put injector cleaner/gas treatment in like 2 weeks ago. could this have fixed the prob? Just acting as a bandaid? Or the calm before the storm? The light did not blow out b/c it still comes on when I start thetruck. You guys think it's something that should get done tomorrow or can it wait till next weekend? Thanks in advance

 

It could be just an 02 sensor. But check the plenum before you put on a new cat. And pull the spark plugs and see what they look like also. And if you have a infrared temp sensor you can check the cat that way. Should be 50 or more degrees hotter on the backside then it is at the inlets.

 

Plugs, wires, dist cap & rotar are all newish April 5th then I changed the plugs to autolites a week later when I changed the oil. The cat sounds like a can full of pennies so it has to go regardless and I was going to do the o2's when I did the cat anyhow. On Monday I will check the plenum when I put the new air cleaner on.

Question about the cat. Hi-flow vs. reg flow? I don't want the truck any louder and I'm not racing around in it, 65 is about the fastest I go anymore. Dose one effect sound or gas mileage more than the other? I'm not trying to gain mpg but I also don't want to effect it in a negative way. It has a flowmaster muffler don't know if that makes a difference. I can't tell which one but can try to get the #s off the bottom of it.

 

I just installed a Magnaflow cat and I have Flowmaster cat back and it is alot louder with the Magnaflow on. Too loud really. I see blue lights in my future. LOL