[rickard681]

I put a 2004 Chevy RamJet 350 FI crate motor in my '69 Nova. My idle always was a steady 610 RPM and 690 with the Vintage Air on. Suddenly my idle changed to 500 / 510 rpm and she began stalling when started cold. In other words, no fast idle upon startup.
I'm thinking idle control valve or maybe a O2 sensor failure?
Any thoughts / input would be greatly appreciated.

 

[Pmotion]

I would check the throttle plate to make sure it’s clean/not gummed up first and clean it if needed. Can you get a scanner to look at sensors? I’m thinking idle air control or coolant sensor issue.

 

[Chris Sengers]

The fuel injection controller controls the cold idle, but it needs a reference,
I would change the coolant temp sensor so the controller knows how cold it is.
Also, there might be a timer in the controller that uses a logic card that says it has been running for x amount of time, the input from temp sensor does not make sense, so it changes to closed loop operation based on time to keep it running.