Idle problems

[apagnozzi20]

So I finally got my car back together and I'm having a bit of an idle issue, it's an 89 foxbody with a 2.3 turbo swap running an la3 ecu, big vam and a top mount intercooler. When you first start it up it won't idle for crap, it will only stay running if I hold it at around 1,500-2,000 RPM for about 5 to 10 minutes. It drives around fine after that but then it will idle pretty high hovering around 2,000 RPM. It's got a brand new IAC and new connector for the IAC. I've tried swapping with other IACs that I have as well as a new vam meter, no change from the old, and a new ECT sensor, again, no change from the old, Here are the codes that I pulled running a key on engine on test.

Code 12 - Idle Speed Control motor or Air Bypass not controlling idle properly (generally idle too low) – ISC

Code 21 - Engine Coolant Temperature (ECT) sensor out of range – ECT

Code 25 - Knock sensor not tested (ignore if not pinging) – KS

Code 26 - Mass Air Flow (MAF) or Vane Air Flow (VAF) out of range – MAF VAF

Code 34 - EVP – EGR did not respond properly during test – EVP

Code 41 - System lean – Fuel control

I checked for vacuum/boost leaks and nothing is leaking. I'm just at a loss and don't know where to go from here, any suggestions are greatly appreciated. Thanks!

~Anthony

[Stinger]

Codes aren't erroneous so if live codes are showing up (not memory codes) then there is a problem with that circuit. You have to understand that wiring issues can cause the same codes as failed sensors though so replacing a sensor won't fix the problem when it's actually wiring that's the culprit. So you'll have to use a multimeter to test the wiring for those circuits. You'll likely find some that are not wired properly. Codes 12, 21, and 26 are the ones you need to concentrate on.