Hi from So Cal

[gregs78cam]

With the engine warm and a start-up in park (P/N grounded) the ECU locks.......

This is what I was replying to. I was making a more generalized comment. Usually a shift into gear IAC counts go up.

[EagleMark]

Yup your right, I thought I conveyed that. No doubt, not disagreeing. You can even see that in others like $0D and my Vortec truck. You'll even see that with P/N wire open/Not grounded. But with idle RPM being kinda varible and always higher then desired idle setting in 1227747 and other C3 ECMs in P/N compared to Drive it never happens that way. In P/N idle is always higher then Drive no matter what Desired Idle is set at or if cold or warmed up or even after driving then letting idle in park. So when going to drive, Idle RPM and IAC counts go down, even though your right, the IAC counts should go up, but since idle RPM also changes from PN to Drive because of the IAC logic it does not show up that way in data.

It drove me nuts for long time on conversions partially because everyone hooked the P/N wire to ground, other websites, AFI, Painless... Until I compared to a factory 1227747 vehicle and found the same thing except PN wire is not grounded in Drive and all of a sudden Idle RPM was where I set it in bin. You would never notice the Idle RPM is higher without a tach or watching IAC counts in stock factory system because it works fine in drive and manual trans the PN wire is open/Not grounded.

[jeepaddicted]

You know what? I just figured out why people have so much trouble getting Min Air Setting done. It's always done in P/N, but when done and checking should be done in D. They set it correctly but when IAC is plugged back in Idle and IAC counts are not correct because of the P/N or D IAC logic!

Exactly the problem I was having. I Used a Howell wiring harness when I installed the SBC 1227747 TBI in my Jeep and it had a connector labeled "PARK NEUTRAL DISCONNECT May Be Emission Requirement" I disconnected it with it in park and all went well with the min air setting.

[EagleMark]

That's funny, Howell instructions too?