So, I had the plenum gasket failure symptoms. At idle it would vibrate forward in the drive-thru. At 35-40 MPH it would just shake up & down. So, I was about to order the Hughes repair kit when I did a tune-up. Plugs & wires, oil & filters. All my symptoms went away. Even the 'Check Engine' light went out.
Well, one day about a month later it just lost power & wouldn't run. So, I thought it must be the Plenum. So, I bought the Hughes kit & did the job. Started it up & same problem. It idles really rough, when you give it gas & the RPMs get to about 2000 it dies.
Head gasket?

 

Clogged cat?

 

^^^^^^x2 for the clogged cat....you will be surprised how bad and quick it does that. my brothers truck drove to walmart fine and then wouldnt move out of the parking lot all in about a hour. after hours of us drinking and being pissed we found it to be a clogged cat

 

Pretty much. If you had to do the plenum gasket, you need to replace your cat. All of that oil and crap gets thrown into your exhaust. A clogged cat means a choking engine. When one end of the air pump is messed up, the entire system fails.

 

Agreed. Read my thread about how badly my truck sucks in the snow. It bogs down and nearly stalls. Temporary solution is a "colander cat" but after the first of the year it's going in for a new cat at a local muffler shop ($400).

Unfortunately, the damage is done to my motor. Depending on how long you ran with the plugged cat and bad plenum, your motor may be toast as mine is.

 

Must one CHANGE the cat or can it be cleaned out?

 

I doubt it can be opened up and cleaned out.

 

you can either replace it to maintain emissions compliance or gut it, as in - turn it into a hollow tin can.

it cannot be cleaned or serviced.

to prove that the cat is the problem, temporarily remove the front o2 sensor to relieve backpressure. if it runs a little better - its the cat.

 

Having to go to walmart pisses me off and make me want to drink.....

 

I just bought my truck a couple days ago, and the previous owner drilled holes in the cat cause it was clogged (guess I have the plenum problem too), said I could just run a straight pipe in place of the cat. Would this cause any negative affects on the motor due to less back pressure?