I've been having an idling issue with my 5.2. Its been idling high around 1250rpms at park and when it's in drive it idles at about 800. Sometimes it's constant and sometimes it'll surge. And other times it'll idle like it's supposed to. I've tried listening for vacuum leaks but I can't hear anything. Any ideas?

 

What are you driving??

 

97 dodge ram 1500

 

Pull the air filter housing off, crack the throttles wide open, and have a look down there. See any oil? If so, blown plenum gasket. See the stickied thread at the top of this forum, (end all, be all, plenum thread) for more information than you would ever want about this issue.

 

I replaced the plenum about a year and half, almost 2 years ago. But when I look down in there, there's not oil pooled up in there but there's light brown spots only in the very back. And the rest is pretty clean other than what the pcv valve spits in there

 

What is manifold vacuum at idle?

 

It could be the pcv valve, They leak and cause the idle to go up.