Hi everyone. my truck runs at about 1100-1200 at start up when it gets warm it only goes down to 1000. I checked for vacuum leaks and the only thing I found was, if i block the crankcase vent (tube off the air breather) it runs like it should (7500rpm). this thing is sucking a LOT of air threw it. I dont like running it like this but i dont like it clunking into gear eather, or pulling when i try to stop. any ideas what is causing this? thanks

 

Which way? Into the engine? Probably blown plenum.... still, shouldn't idle that high. Might try cleaning the throttle body really good first.

 

ya i did that even with a tooth brush, changed pcv as well

 

its sucking air into the valve cover

 

if it was the plenum would spraying brake clean around it rev the idle up

 

No. Plenum leak is internal. You get serious suction from the crank case.....

If it is REALLY blown, that would account for the high idle. IAC simply can't compensate for a large leak. You burning a great deal of oil?

 

Might want to pull the TB again and look in the intake to make sure there isn't any oil pooling down there. If so, it's a classic sign of a blown plenum gasket (in which case, they make an aluminum plenum plate to go on the bottom of the intake to permanently fix the problem). Someone in here probably knows a simpler way, but from what I understand, just simply peeking down the TB isn't accurate....

 

yes as a matter of fact it does seem to burn a lot of oil

 

i never pulled the tb but i think i might

 

Your plenum is indeed blown. Start collecting parts for the repair. Check out the Plenum thread stickied at the top of this forum for a good list. If the truck has a lot of miles on it, (over 90K.....) good idea to do the water pump, and timing set as well, as it is only about six more bolts, and there you are.