That is the question. I recently became a Ram owner, and lover. Consequently, a new member of dodge Forum as well. Hope I m doing this right.
After reading the Plenum sticky I feel like I need to replace my plenum. I bought a 99 1500 Ram with 104,000 m on it for $1700. It looks good and is a quad cab so I wondered why so cheap. Well two days later, it wouldn't go faster than 30 or 2000 rpm's. After a full day of research I cut off the cat and straight piped it. It worked. Now ive removed the num 8 spark plug and it was covered in ash. SO, do i need to do the plenum thing or not?

 

It's quite likely that you need to replace that gasket. Check out the sticky here in the forum for far more than you ever wanted to know about it, including some hype and mythology for added flavor.

 

only replace it if you have pinging, or oil usage and oil pooling visible in the bottom of the plenum.

if you have pinging, sometimes you can run 89 or 91 octane to avoid the ping and buy some time.

 

I would just replace it and get it out of the way when you have the time and $ to do it. Also the other associated things- inspect and/or replace - cap, rotor, plugs, wires, water pump, stat, all hoses, timing chain, etc.

 

First thing I would do before you do anymore is a compression test. Since your cat was clogged badly, could have further damaged the engine heads. Good chance he knew about the issues but couldn't diagnosed them or repair them so he sold cheap.

If the engine is still good, might have gotten a good deal. If not, well get the wallet out.

Brad

 

Yep. Those symptoms describe a clogged cat. Were it me, I'd get completely **** redundant and yank the engine for a complete rebuild, including the plenum, and I'd install a new exhaust system. Replace both O2 sensors for sure.

After that, you'll have a dependable, durable running truck.

 

Until the trans goes out due to the....


SHEER AMOUNT OF MANLY POWER the engine makes now.

 

is there no one piece plentum as a replacement

 

Hughes Air-Gap intake, or Chrysler M-1 manifold. Those are the only two options.

 

I had ash and oil on the #8 plug and one year after plenum fix I have no ash and oil and no money...glad it's fixed
Don't forget to replace tb gasket, rotor cap and button, thermostat hose, and new plugs and wires while you are in there.
My next fixes will be new exhaust system including headers and getting rid of the stock air intake. I'm so tired of fighting with it to get it back on right!