KillverCity

The car is bone stock. No issues for first 3k miles. Then under normal cruising speed of about 35 with low RPMs my check engine light pops on.

Each time I take it in, they run a relative compression test, EEC test, and check the injectors. Each time they say everything is fine. I usually get about 80 miles on the car before the check engine light returns. I am not experiencing anything performance-wise. No trouble on startup.

The third time I had it in, they swapped the components from cylinder 8, with cylinder 7. They drove it for about 70 miles and the same code trips. "P0308".

They decide it must be the injector. Replace injector.

Got it back on Monday, check engine light by Wednesday. This is my 4th time with it back to the dealership in 3 months.

Anyone else experience this?

JimC

Ask them to run the crank relearn process if they haven't done it. Maybe something got "lost" in the program.

socal57chevy

What are the results of their compression tests? "Good" is not an acceptable answer...ask for specifics.

darkmach1

Time to start looking into lemon law bro

redass02gt

Try a different dealership if possible. This one clearly doesn't have an ace mechanic to turn to for tough problems.

barstowpo

Coil or plug? Intermittent coil problems are difficult to trace. That must be why they swapped stuff.

KillverCity

Still waiting to hear back from Ford.

Yes the measurement they gave me for the compression test was "good". I will push for specifics.

socal57chevy

That usually means that they wrote on the back of the RO to get paid for the diagnostic time, but didn't actually do it. lol
I always write the results on the back of the RO and show the customer.
I've seen the Toyota 5.7 break a valve spring and the cylinder pressure will push the valve closed some of the time leading to a sporadic misfire on that cylinder. Sometimes it seals, sometimes it doesn't. If it isn't caught in time, it's just a matter of time before the piston smacks it and things get really ugly.
Weak coils can be hard to pin down, like barstowpo mentioned, but a lab scope will find a weak coil every time.
They need to put a different tech on your problem.

KillverCity

They just got back to me. They are saying they plan to replace the cylinder head.

movielover40

There you go.

If this doesn't work ask for another car.