2003 f150 5.4, 150K


Symptom:

Sporadic “shivers” through the engine, only during idle. Felt in the cab as a light shaking.

Problem occurs at 600-700 RPM, runs perfectly 700 +. No hesitation, stalling, or any drivability issues.


The front o2 sensors cycle properly

Rear o2 circuit is recently messing up, but is not of concern.

The computer detects no misfires

Mass air flow reading is around 0.59 lb/min at idle and increases with throttle movement


The problem has been around for about 3 years, it is getting worse at an incredibly slow pace. Due to various breakdowns over the years, I’ve replaced these parts:

Timing chain, tensioners, and guides (with head gaskets)

Cam and crank position sensors

Intake and throttle body gaskets (all 6)

Idle air control valve

Throttle position sensor

Every vacuum line has been thoroughly tested or replaced (including that annoying one behind the intake)

PCV valve and grommet

EGR valve and solenoid

All o2 sensors

Fuel pump

Spark plugs and boots

Air/fuel/oil filters


I kept hoping I’d hit two birds with one stone through all of that, but the idle has been constant


The pic is a hack-job screen shot of PID values




Going to bite the bullet and take it to the dealer for a PCM update here shortly, maybe see what black magic they can work on the computer. But I’m fresh out of idears for now, any suggestions would be appreciated!

 

Read this:
https://www.autoserviceprofessional....for-you?Page=2