High Idle IAC TBI - The 1947 - Present Chevrolet & GMC Truck Message Board Network

tommr86 · 02-09-2023, 11:03 PM

90 Silverado TBI is Idling around 1200. Traced to IAC. Did relearn procedure. Idled down to 650. Shut truck off. Restarted and its back to 1200 rpm. Changed IAC. Did relearn. Idle comes down but goes back up after shutdown and restart. Same as original IAC. Installed new Coolant temp sensor and thermostat. Timing is set. Idle stop screw on TBI unit has never been touched. Did smoke test and zero leaks. Excellent fuel pressure and regulator tests fine. Would this be a bad ECU? Thanks

02-09-2023, 11:03 PM	#1
tommr86 Registered User Join Date: Jun 2012 Location: levittown pa Posts: 4	High Idle IAC TBI 90 Silverado TBI is Idling around 1200. Traced to IAC. Did relearn procedure. Idled down to 650. Shut truck off. Restarted and its back to 1200 rpm. Changed IAC. Did relearn. Idle comes down but goes back up after shutdown and restart. Same as original IAC. Installed new Coolant temp sensor and thermostat. Timing is set. Idle stop screw on TBI unit has never been touched. Did smoke test and zero leaks. Excellent fuel pressure and regulator tests fine. Would this be a bad ECU? Thanks



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