Fix high idle speed – Ford
If you have a high idle Ford or Lincoln Mark LT truck with the 4.6 or 5.4 engine, this may be your fix.
Ford has issued a service bulletin to address a high idle Ford problem and an intermittent hard start condition. The problems may also set a P0606 trouble code. This may be caused by software issues. To diagnose the problem, clear the codes and run the standard KOER tests. If the code resets, this bulletin doesn’t apply. However, if it does reset, DON’T replace any parts. Get the software update.
Get your vehicle reprogrammed at any FORD dealer or independent shop that’s has reprogramming capabilities. The charge should be less than $150