like i said in the title i have a weird rattle that sounds like its comeing from inside my dash it only does this tho around 1800 rpm any ideas on what this could be??

 

PLENTUM PING run a higher grade fuel and report back and tell us its fixed

 

thank you for the reply i will give it a shot and let ya know

 

check the pcv valve on the pass side valve cover while running.... they rattle like that when they are bad....

 

can you give me a idea on what it looks like how to get to it and how to tell if its bad....honestly i have no idea what it is

 

it looks like this, with only the white part sticking out. Look on the passenger side valve cover, it'll have a hose connected to it. Listen to it and feel it while the truck is running. Maybe rev the truck up a little too.... it might not be your rattle, but it fixed mine...

 

the pcv valve was fine............ gas was also not the problem.......any more ideas lol??

 

your plenum gasket could be leaking in turn causing a chain reaction of problems leading to a spark knock. witch is the rattling sound u could be hearing.

 

Sounds like it's pinging. Most likely the plenum gasket. Look into your intake manifold and see if there's oil pooling.

 

Does it do it more when the engine is under load (ie going up a hill or passing someone)? Are you burning oil? I'm betting on the plenum gasket or a vacuum leak. I had a leaky plenum, craked vacuum lines and a couple of bad vacuum check valves. When I would give it the gas going up a hill, the valves clattered and the AC quit blowing. It also was burning a lot of oil and the hubs had trouble unlocking. But, it was pretty clear the clatter was going from the engine and not the dash.
Like they said, take the air cleaner off and look into the throttle body with a flash light and check for oil and goo. If that's not the plenum (and even if it is) check the vacuum lines coming off the manifold to make sure they aren't cracked.