This weekend I noticed a rattling from under the truck...hit the cat with a hammer when it was cold and heard rattling, so i assume its shot. My question is would the cat being clogged cause a check engine light? Cause I ordered a new cat yesterday should be here this week, and then tonight I floored it merging onto the highway and it kinda hesitated and then went fine but the check engine light flashed and is now on steady. Code reads PO300 random cylinder misfire. Truck runs fine. Just seems ironic that i just noticed the cat is shot and the light came on today...should i assume its a related issue or could something else be wrong??

 

theres a chance its not running as fine as you think since you say it did hesitate.......could be from the cat....did you clear the code?

 

cleared the code and drove it 30 miles and it didnt come back the truck feels fine....im afraid to floor it again though as that is when the light came on...im just wondering if its a coincidence or if two different things are going on here

 

i figured that maybe you caught a chunk of it, but not sure if that sudden extra backpressure would cause the code or not

 

If the cat is bad, then it's pretty much a guarantee that the plenum gasket is blown. And if not fixed , the new cat will slowly but surely be destroyed. Replace atleast the front 02 sensor as well.

 

I have ordered new oxygen sensors so I do plan to do them as well....why do u say that the plenum is shot? I am aware of the symptoms and doubt it is shot.

 

From my own experience and others I've seen. Those symptoms you know of are when the leak gets real big. A smaller leak won't show itself like that, but will in time ruin the cat.

 

So In other words if you think the plenum is ok its really not. I'm sure mine is on the way out the door at 51,555.

 

As far as I'm concerned, the only way to know for sure is to tear it apart. And since his is a 97, I'd say there is real good chance it's blown, not to mention it might have the death flash helping mask it.

 

I though he got a chip of it. I know I did and I love mine. Can you say blown gasket for sure! I sure can lol.