I have a 2003 ram qc with the 5.9 magnum. I was wondering what are the signs of a plenum leak? Currenty the truck has 70k on it and is well maintained, always put 93 in and mobil 1 from 20k on. The last year or so i have had a ping issue when i give her full throttle, when i put the programmer on 93 it gets worse(hypertech). My mpg is about 11.7 and has new plugs, cap, rotor, wires routed correctly, and headers. Other than that its stock. Would a blown plenum gasket cause the ping to be random and mostly once the truck is warmed up? My heads are fine no cracks, looked down the tb did not see any pool of oil and it really don't burn any every 5k i get it changed. Also i have seafoamed it twice with no smoke to see coming from tailpipe.I just would like to know before i pay my mechanic $500 to replace the plenum gasket, and to those who have changed them did you notice any power coming back?

 

Take the throttle body off and look down the intake manifold for oil pooling. If there is a thin layer of oil film, you are in the ok. But if you see oil pooling, you have a blown gasket.

Dont pay your mechanic $500 to just replace the gasket when you can fix it yourself, forever, for $200. $500 is insane.

 

If you do end up having a mechanic do it, tell them you want to buy a kit from Hughes Engines and have them install it...not just factory replacement parts.

http://www.hughesengines.com/Index/p...2&partid=22220

 

whenever it says Dodge on the back.

 

Lol...that's funny right there, I don't care who you are.

 

haha!!! On the floor loling haha!!!!

 

Simply looking down into the intake manifold will not give you a definite answer. I thought my plenum was fine when I looked down in there and I didn’t see any oil. As it turned out, the gasket was completely shot. I bought a $10 vacuum gauge from Harbor Freight and tested the vacuum according to the TSB. Doing this test assured me that my plenum was toast.
Here were the symptoms with my 5.9
-when revved it returned to idle slowly (took about 4 seconds)
-once in a while blue smoke you pour out of the exhaust on startup
-burning quite a bit of oil, about 1 quart every 600 miles
-lots of spark knock (pinging) under moderate to heavy throttle (ONLY WHEN WARM)
-11.5mpg no matter how I drove
-The truck felt sluggish when cruising down the highway
Now that I fixed the gasket all of these symptoms are gone.

 

Thanks for the replys!! So maybe its not the plenum, what else causes spark knock (pinging)? It only does it when its warm, floored, and even worse on the 93 program. Could a bad o2 sensor cause it?

 

thats a good one lol!!

 

A bad plenum. You need to check it before you rule it out.