[TransAm400]

It's been awhile since I messed with it but I did get it running better. I think reducing the idle timing helped. I believe I ended up around 16 degrees. The AFR at idle is close to the target and it is going into closed loop learn now.

I do still have an issue with the RPM's hanging up when I let off the throttle. TPS and IAC are at 0% but RPM will hang around 2,000 until I blip the throttle and then it will return to normal idle. That has been pretty annoying. I only drove the car a couple times in the past months since it was 100+ degrees all summer here in Houston. Looking forward to getting it out more now that it has cooled off.

[JLMounce]

Originally Posted by TransAm400

It's been awhile since I messed with it but I did get it running better. I think reducing the idle timing helped. I believe I ended up around 16 degrees. The AFR at idle is close to the target and it is going into closed loop learn now.

I do still have an issue with the RPM's hanging up when I let off the throttle. TPS and IAC are at 0% but RPM will hang around 2,000 until I blip the throttle and then it will return to normal idle. That has been pretty annoying. I only drove the car a couple times in the past months since it was 100+ degrees all summer here in Houston. Looking forward to getting it out more now that it has cooled off.

Something is going on with that. Throttle blade adjustment, issue with the IAC, vacuum leak or all of the above.

If your throttle is closed and the IAC is closed, the engine should darn near stall.

[HWYSTR455]

Or the throttle blades are hanging up. Is the throttle return spring too weak? Is the throttle cable hanging? If it's not fully closed when you turn the key on it will use whatever position it's at as 0% (TPS autoset occurs at every key-on)

If the IAC AND the TPS are at zero, sounds to me that the throttle blades aren't closing all the way, and it's referencing the open position as 0%. Maybe take the throttle body off and check to see if there's any witness marks on the gasket etc, and that they are near closed.
*
Any exhaust leaks?



.

[JLMounce]

Originally Posted by HWYSTR455

Or the throttle blades are hanging up. Is the throttle return spring too weak? Is the throttle cable hanging? If it's not fully closed when you turn the key on it will use whatever position it's at as 0% (TPS autoset occurs at every key-on)

If the IAC AND the TPS are at zero, sounds to me that the throttle blades aren't closing all the way, and it's referencing the open position as 0%. Maybe take the throttle body off and check to see if there's any witness marks on the gasket etc, and that they are near closed.
*
Any exhaust leaks?



.

Good call on the throttle hanging up. My system did the same thing when my throttle cable started binding in its sheath.

[Formulajones]

On the holley it's pretty common to have the rear blades hang up. Sometimes after they are run a while and go through some heat cycles things move around. Sometimes it's apparent right away.

It's an easy fix. You can have a look at the blades and make sure they are centered but most just give the rear throttle blade spring another wrap around the shaft.

https://youtu.be/avRqQZBOxP0

[TransAm400]

Interesting. I'll check out the secondaries first. I also have an extra IAC on hand I can swap out if needed.