Hey guys, Im having some trouble with my idle on my '96 ranger 3.0 5 spd. This morning I fired it up and the rpm was very high, (I don't have my tach in yet so I can't tell you exactly where it was.) Anyway, whenever I was at idle, the rpm would climb, including shifting and sitting at red lights. Whenever I had the clutch engaged, the rpm was okay, but it seemed a little low to me. I drove to and from school like this without getting a CEL.

I tested the IAC by unplugging it and the rpm dropped to about where it should be. I drove it around the block with the IAC still unplugged and it ran great. I also tested the IAC voltage and it came up fine. After playing with the IAC for a while I started it up and finally got a code P1504 Intake Air Control circuit malfunction. I searched all over but it seems like no one else has gotten this code before. What would the circuit malfunction mean? I'm thinking its the IAC itself...

Any ideas?

 

Assuming that here are no other vacuum leaks, it sounds to me like it's defintely IAC related. When you unplug the IAC at idle the engine should struggle to stay running and maybe even die. The idle shouldn't return to normal.

P1504 is the kind of code that would be set if the IAC was unplugged.