I replaced the IAC valve on my 97 Dodge Ram 1500 with the 5.2L, 318CI engine and 5 speed manual trans due to a “check engine” code. Before installing the new valve, I cleaned the valve seat in the throttle body and checked for vacuum leaks. After restarting the engine, the check engine light did not return but it seemed to be idling high even after warm up. Does anyone know what the curb idle should be for this truck? Any other areas to check for? Thanks!
Try disconnecting the wiring to the IACV while idling.
The idle should drop way down and maybe stall.
If not, there’s too much air getting past the throttle butterfly, or there’s a vacuum leak you missed.
Thanks for the reply. Ill disconnect the wiring to the IAC and look for an RPM drop. If no drop, what then? Will a vacuum gauge indicate a vacuum leak? I understand this engine had no valley cover between the cylinder banks but used a 2-piece intake manifold that had a separate plate screwed to its bottom to take its place and that it has been known to leak and draw oil into the manifold.
While idling, disconnect the the breather hose from the left side of the air cleaner. If there is a strong vacuum, the intake manifold belly-pan is leaking.
Thanks Nevada…I was wondering how to diagnose that. I wonder if that was a common problem for all 318’s with this type of manifold or just certain years? I understand someone manufactures a replacement bottom plate for this manifold that will solve the leakage problem.
I believe the early Magnum engines used a paper gasket on the belly pan that failed.