High/Hanging Idle - ZR-1 Net Registry Forums

ssmith95 · 3 Weeks Ago

Hi Folks. Just picked up a 1990 ZR1 #1476 this past weekend and on the test drive the car was hunting for idle, but RPM would settle to an appropriate level. After stopping, idle would fluctuate for a bit, then eventually settle. I figured the car had a vacuum leak, but the hunting has turned into a consistently high idle ~1400 rpm. A datalog with TunerPro shows 0 IAC counts and covering the airhorn fails to stall the engine out. With the airhorn covered, I can hear a "chirping" sound but can not locate it.

I've read through "Finding and Fixing Vacuum Leaks" and repaired the lines coming from the dual vacuum fitting on the front of the plenum. The MAP sensor and PCV valves are free of leaks, and the throttle body was serviced by Marc Haibeck 10k miles ago according to receipts I received with the car. Car also has a tune from Marc.

Anything else I should check before I pull the trigger and pull the plenum?

3 Weeks Ago	#1
ssmith95 Join Date: Oct 2024 Location: Texas Posts: 13	High/Hanging Idle Hi Folks. Just picked up a 1990 ZR1 #1476 this past weekend and on the test drive the car was hunting for idle, but RPM would settle to an appropriate level. After stopping, idle would fluctuate for a bit, then eventually settle. I figured the car had a vacuum leak, but the hunting has turned into a consistently high idle ~1400 rpm. A datalog with TunerPro shows 0 IAC counts and covering the airhorn fails to stall the engine out. With the airhorn covered, I can hear a "chirping" sound but can not locate it. I've read through "Finding and Fixing Vacuum Leaks" and repaired the lines coming from the dual vacuum fitting on the front of the plenum. The MAP sensor and PCV valves are free of leaks, and the throttle body was serviced by Marc Haibeck 10k miles ago according to receipts I received with the car. Car also has a tune from Marc. Anything else I should check before I pull the trigger and pull the plenum?