Ok that makes more sense. The needle started at zero and dropped rapidly to 20, which means my plenum is good right? So now where do I go from here?

No I haven't pulled the #8 plug since I changed them 2 months ago. (I haven't been able to find my socket wrench extensions) Tomorrow I have the day off so I'll pull the plug and inspect it, my guess would be that it's toast again, since the pinging hasn't gotten any better since changing the plugs.

If the #8 injector was really that bad, wouldn't it be running crappy and throwing codes? It idles and drives great, there's just a lot of loud pinging. I'll unplug the injector tomorrow and see what happens.

 

I just checked the oil level last night and it doesn't look good. I'm burning a LOT of oil. About a half a quart per week. I know I'm lot leaking oil because the underside of my truck is spotless. Tonight I'm gonna do another vacuum test, pull the plugs, and mess with the injectors. I'll report back later tonight or tomorrow.

Another question about pinging, could incorrect spark wire routing cause pinging and fried plugs? My plugs aren't routed according to the tsb, and I'm wondering if that could be the problem.

 

Any chance you can post a pic of your gauge?

 

WOW did you read the same TSB I read?
It states to let it idle for 30 seconds after everything is connected and capped then check for a vacuum. If there is a vacuum present then you have a blown plenum gasket acting like "a PCV system" when yours is all capped.
It says not to let the engine get over 3 psi because you are disabling the PCV system... not the other way around.

 

Ok I'll make this simple... for YOU... if you have a source of vacuum with the PCV system blocked off YOU HAVE A BLOWN PLENUM GASKET.
With the PCV system blocked off you should be building pressure if there is no leaks.
In reality you should not need the aid of a gauge for such simple test, just block off the hole PCV system but put your finger over the most convenient hose, rev up to 2k then "FEEL" for a vacuum or press.

 

Gus got it right, even in spite of "HELLO MY NAME IS GUS The AS$HOLE with the underpowered cheap sound system the awfull BFG mud terrain tires and the stupid plenum idea that will never work."

Mine was leaking oil into the intake even though I didn't have any vacuum in the crankcase, so the vacuum test only indicates a large leak. When I took mine apart the gasket was bulging out in several places and was ready to break. There was a $hit ton of oil in the intake when I busted off the plenum pan.

 

My engine would rattle and ping so bad accelerating under load I thought it was a lost cause. I set the stock champion spark plugs gap to .050 from .040 and it has completely eliminated the pinging and gas mileage has increased 4 to 5 miles/gal. Also used bottle tecron injector cleaner with about 1/4 tank of gas,added 10 gallons another bottle tecron and drove it to empty. I've already rerouted new plug wires,new cap and rotor,put 91 octane in the tank, but nothing worked as good as changing the plug gap.