Low idle, 411 and 412 codes KOER

[Will Presley]

Hey, folks! I have '94 Eddie Bauer 4x4, 4.0L OHV. I recently fixed a bunch of air intake issues that were causing a lean condition. The truck ran great for a while, but now it's running rough again. I did an idle relearn procedure, which helped for about a day. Now the truck is running with a slightly low idle, and it's running rough. No check engine light, but I did the self test and passed KOEO, though I got codes 411 and 412 for KOER. I've checked for vacuum leaks and can't find any. I've replaced the IAC about 5 times, so I doubt that's the problem. Any ideas? Thanks!

 

[MrQ]

Clean out the throttle body. Your IAC may be working, but if the passages are clogged, it really can't do much.

 

[Centaurious]

Seconded! While you are at it pull the EGR Valve and ream out the passage behind it, It actually is about 1/2 inch in diameter.