01 K1500HD-6.0L Automatic
(full tune done at 100,000 km's truck now has 130,000km's

Just got the truck a few days ago.
First I notice when she is started I get some clacking and ticking for about 15 seconds wich I have been told is expected of these motors.

In the morning after siting all night I notice the first couple throttle's down the alley it almost misses/luls a little. As soon as you give it half throttle it goes away and runs good after about 2 mins of driving.

Today I was sitting after driving it down the highway and I was at a stop light and revved it up to 2500 rpms and got a really tin/knocking rattle.
I got out and revved it right to the limiter as it idles down it rattles loud.

My dad tracked it down to one of the cat's (the smaller one that is about the size of a 2 litre) When the your cats are bad do they cause any of these symtoms?

I live in Canada and in my province there is no emmisions testing. What converters can I take out and put straight pipes if any at all. I don't want the engine light on after taking some if any at all out.

 

tickin in the morning is common because of the lifters tapping. that will stop shortly. s for when its warm and ticking, i would assume parts are becoming warn and ticking.

 

Yeah no ticking/clacking once its warmed up.

Just the first couple accelerations for a couple minutes of driving in the morning seems to be a little tired almost like a person waking up.

Idk haven't had one of these newer trucks in a while. I'm used my TB injected 1995 350 were the throttle responce is right there hot or hold at a snap of finger.

 

Put some Lucas Oil additive with a fresh oil change and see if that helps. Some internals may be gunked up.

 

An oil change is deffinatley going to happen tommorow.

Next will be figuring out what the rattle/tin heat shield sound is after you rev it and the motor slows down. Thought it was my bottom end knocking at first.

I think this truck has like 5 or more catylitic converters/resonators.

 

They previous owner always did his own oil changes and used castrol 5W30 conventional oil wich is what it says on the filler cap. Is that a good oil to run/weight or should I change as fall and winter are coming up here in Canada.

 

The converters on these truck seem to have a lot shorter lifespan than the older trucks for some reason. I have replaced more on the 99 and up trucks than all the previous years. They will rattle, but that could be just a weld on the shield that needs to be retacked. Take it to a muffler shop, they shouldn't charge to check it and if it is just a weld it shouldn't be more than 10 or 15 dollars.

 

Those cats get pretty hot so the insides sometimes tend to come apart. When they do, it sounds like the sound you are describing.

 

(while cold) get under it and hit the cats with either your first or a rubber hammer (softly). you'll be able to hear the innards rattling if thats your problem.

 

Took her into the muffler shop after work.
Massive rattle actually in the muffler.
Hit the cats with a rubber mallot and they are all perfect.
Both cats have 02 sensors going to them.

Next think will be to diagnose the first acceleration in the morning being kinda of a lul and nothing being there. I guess I can live with that though. Just glad its not my bottom end exploding.