On initial start up during warm up cycle, The engine will surge from 500-1200 in park and driving. No codes or check engine lights, After warm up no issues. Replaced air idle, throttle position, mass airflow sensors. slowed serge to 200-300 rpm. Did not find any vacum leaks. Throttle position and air idle sensors had carbon deposites.
??There are two types of DTC's, 1 trip DTC's and 2
trip DTC's
??A 1 trip DTC is for a condition that requires
immediate attention such as a catalyst damaging
misfire.
??A 2 Trip DTC is one that a condition must be found
during 2 consecutive trips such as an EGR fault.
??Most Monitors do not set a DTC and light the MIL
when a vehicle fails a test for the first time during a
DRIVE CYCLE. If a test is failed on a second
consecutive DRIVE CYCLE the MIL will light and a
DTC is stored in the vehicles powertrain control
module (PCM).
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5.4L gas
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