I have a 91 K2500 with a 350 5 speed, It has the engine out of a 89 c2500 but it originally had a 350 as well. It seems to idle at around 1100 to 1200 rpms. I have heard this is a common problem. What would be causing it? It also has a ticking noise on the right front of the engine, sounds like its external any ideas? any help would be great. thanks

 

That ticking could be an exhaust leak from the manifold.

 

Well it sounds more like a metal to metal clicking actually. Also does anyone know where the oxygen sensor wire comes out of the cab at? The wire has been tore off and I cant find where it goes. thanks

 

Well a small exhaust leak sounds exactly like a piece of metal tapping. But just a thought.

 

i agree culd be an exhaust leak i had the same sound on my 91 chevy 1500 5.7 could be the donut gaskets thats what my problem was