I just replaced timing chains on my 5.4 24v engine now after about 30 mins of driving the engine struggles to run as if not running on all cyl at hwy speed ok but in stop start traffic not good
Coil packs replaced, had new spack plugs replaced about 3 years ago
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Answers & Comments
Check the valve timing as it indicates a timing problem.
the higher rpm at highway speed indicates that the valve timing is coming correct as the rpm advances the timing in the solenoid actuation but at idle it is out a bit
could be one cam off a tooth
run the fault codes to see if the cam shaft advance operation is working ( wiring , cam shaft position sensor , actuator etc )
check the fuel pressure and injector operations as they may be failing at the lower pulse action