Hi There,

My 2003 4.6 V8 explorer has 300K miles but has been well maintained and miles are primarily highway driving.

A few months ago on a long trip I had a solid check engine and then an intermittent blinking check engine light. Never had a blinking one in the history of the vehicle. My repair shop diagnosed misfire in cylinders 3 and 8 and replaced tuning coils and plugs in all 8 cylinders.

No problem for next 1,000 miles, but then had same issue for a short period and then it went away. Took it back to the repair shop anyway and codes showed misfire in cylinder 3. They replaced the tuning coil in that cylinder again and said if it recurred it was likely something more expensive like possibly an injector. It was fine again for the next 2,000 miles then I had the same solid check engine light and one time if flashed for a while.

As I was on a long trip at that point I decided to try two things at the same time, thinking maybe it was an injector-related. (1) I started buying gas only from stations that sell "Top-Tier" designated gas, and (2) I upped the octane from 87 to 89. About 100 miles later the solid light went away and 2,000 miles later I haven't had a recurrence of the issue. I've been running Top-Tier gas 89 octane the whole time.

I don't really understand if there is anything I can conclude from this? Would appreciate any thoughts.

 

My conclusion would be that your mechanic did not perform any relevant diagnostics, but took a guess at you expense and just tossed a load of parts at your engine..

 

Did they use genuine Motorcraft parts?