Rough idle

I have a 2005 Ford F150 with the 3-valve 5.4 V8. Ford has warranted the fuel injectors for 120,000 miles, but will only replace injectors as they go bad. I have had one injector replaced by the dealer after the check-engine light came on. After that occurred I have used only top-tier gas (Chevron and Shell). The F150 currently has 55,000 miles on it and has been serviced regularly by a Ford dealer.

Lately, there has been some rough idling similar to what happened when the injector was replaced, but with no check-engine light. I took it to the Ford dealer, they found no instances of miss-fires and are now trying to sell me on a $150 fuel system service (ie., . Would it be worth getting that service done?

Your misfire has to be pretty substantial to turn on the engine light. YOur SOTP meter may well be more sensitive. They should be able to pick up misfire of a lesser extent with their code readers and it should be cylinder-specific. You get a misfire most often from either the injectors or coils (on plug).

I don’t think you need that service. I think that you are worrying too much about what fuel you use too. You might buy some Techron and follow the instructions.