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When I start a Ford Explorer 4.0 SOHC from a cold start, it will rough idle for 5-7 minutes and I must keep my foot on the pedal. Once it’s warmed up, it will idle smoothly. What could cause this?


Anything from an ECT (engine coolant temperature sensor), a faulty IAC
(idle air control valve), intake manifold or post MAF (mass airflow) sensor
to old, worn-gap spark plugs can cause poor running when cold. Check the
plugs and retrieve any DTC (diagnostic trouble codes) for a more clear
picture of the problem.


Jim O’Neill
Chino Autotech Inc., Auto Club SoCal AAR
SAE Int’l SoCal Section Board of Governors
Vice Chair, Service Technology Programs
NASTF Service Information/Communications Committees
Auto Value/Bumper-To-Bumper CSC Nat’l Council
ASE CMAT-L1, CA. Smog Check Technician
AMI AAM Accredited Automotive Manager

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