A friend of mine his truck is running like crap and we are thinking that the cat is clogged but the codes from the CEL are showing cyl. 3,4,5 misfire and I was just wondering what are all the possibilities that cause cylinder misfires and it runs boggy like the cat is plugged....

 

Bump.

 

Could be a clogged inlet on the injector. Look at my engine threads. I had junk in the fuel rail and a few of my injectors were plugged. A clogged Cat will more than likely cause #6 and #8 to misfire; however, if the truck is running sluggish, that is an indicator. Take it to a muffler shop and see if they will pressure check the enhaust for free. Mine did.

 

Its gonna bog if its only running on 5 cyl. Start with the basics first of course, spark plugs, spark plug wires, cap and rotor, fuel injectors......

 

its running alright just coded misfires when it backfired a few times and whre thinkin its the cat cause its really quiet all of a sudden and its got a flo 40 mock dumped under the bed. umm idk im thinking plugs are instore we are gonna pull em and check em out within next couple of days

 

If it backfired, then yeah, you might have cooked a CAT, they like to melt from backfiring

 

What are you talking about?

 

Sending to much raw fuel through a cat and igniting it can cause the medium to melt and fuse together. This new to you?? Thats why ya don't put flamethrowers on fuel injected vehicles. Or am I thinking of the cats from 20 yrs ago? Don't understand why you would ask that I guess....

 

That is an incorrect blanket statement. Not all FI vehicles have a cat.

 

you know what it might be the cat, it has been like basicly blowing the gas out into the xhaust when the IAC was f'ed up so hopefully when cat gets deleted from the subject motor vehicle the thing runs better.