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Idle Speed On Delphi EFI


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As you know, the Delphi EFI system uses the IAC (intake air control) to maintain the Idle Set Speed
set in the ECM. Engine rpm at idle should be very close to the Idle Set Speed when the engine reaches full operating temperature. V Rod idles tend to fluctuate and a 100 rpm variation is normal. These are dealer adjustments using the digital tech which is basically a laptop computer with HD programing.
To determine if an idle is incorrect go to Data List and compare Engine Speed to Idle Set Speed. If they are within 100 rpm, and an idle speed change is desired, adjust it using the Calibrations, Idle Adjust feature.
If idle speed is several hundred rpm higher or lower than the Idle Set Speed the ECM may not respond to the above process and TP Voltage should be investigated. Why TP Voltage? The answer is that the ECM looks at two conditions to control idle, VSS voltage (speed signal) and TP Voltage (0% throttle position). If the TP Voltage with engine running is higher than with the engine not running, or if the TP Voltage is fluctuating while the engine is running, the ECM sees this higher voltage and assumes the bike is not stopped so will not attempt to control the idle. It is easy to check. Observe TP Voltage with ignition ON, then start the engine and observe it again. Voltage should be the same. Next, look for a fluctuating TP Voltage while the engine is running. If TP Voltage change 02 volts or more, make sure battery voltage, ET and IAT voltages are not fluctuating due to a poor connection. Next, check TPS connections, if ok, replace the TPS.