Hi, I current have a boosted b series motor which has been professionally tuned and all of a sudden I began to run rich at idle... i have checked wiring, sensors, cam timing, ignition timing, leaks, valve adjustment and have sent data-logs to a tuner to revise and make sure tune calibration is ok... everything seems to be fine but still reading full rich a idle unless i unplug iacv valve i will idle 14s or so... compression test turn out fine) and car pulls fine besides running rich all of a sudden and began to pull low vacuum readings of 14-16 hg( reason car a/f's aren't correct... i think) any suggestions?

 

If it's pulling lsess vacuum then you have a a leak somewhere and it sounds like it may be related to the IACV. I wouldn't make any changes to your calibration until you get the low vacuum readings (air leak) fixed.

 

awesome... plastic part where iacv plug connects to on IACV is slightly cracked... don't know if it would cause a leak on that part... i have sprayed starter fluid but did not notice much a difference in rpm... Note: spark plugs don"t look like a car running an a/f of 10.0 from what I was told... fuel pressure reads along 40-42 psi a idle...

(yellow line represents crack)

 

I had the same problem once, damaged IACV cap. It was drawing current from the injectors (same circuit) and threw off the pulse width while the IACV was active. Replace the IACV, make sure there's no wiring faults, that should fix you.