ddog96mn

i have a 2005 Chevy Silverado 4.8L V8 with about 150,000 miles on it, and when i fire it up after its warm, the rpms go up to about 1800 or even 1900 or so. when its cold it goes to about 1400 or so (which i am guessing is normal) my fathers truck (2002 Chevy Silverado 1500 with a 5.3L V8) starts normally, only going to around 1000 rpms. not sure if mine is a big deal or not, but its rather annoying. any help with this problem would be much appreciated. thanks!

delta579

Do a VAC test as it sounds like a VAC leak. 17-20 inches, steady needle. Intake gaskets are mostly culprit. Easy fix, about 2-3 hours.

ddog96mn

how do you perform a vac test?

delta579

Follow the PCV line back to the top of the intake manifold. There will be a short piece of flexible hose connecting the the "hard line" to the manifold. Disconnect here and plug your VAC gauge into the manifold side. VAC testing can detect so many things. A lost art since OBD's came on the scene. Hope this helps.

Jeff Collision

Check your fuel pressure. You will need to use a fuel pressure gauge. The pressure can be tested by just turning the key on after being off for 10 seconds.