Zeegs

Hi, looking for some input.

I have a 2013 with a 5.0 L with just over 100k KM (just out of warranty). A couple weeks ago I noticed it was running a little rough at an idle (just barely noticeable & no codes). While at the dealership for an oil change I got them to have a look, they advised that it needed new plugs. A few days later, it ran noticeably rough and had a check engine light (misfire cylinder #7). I changed the plugs (all the plugs looked good, no signs of an issue), the check engine light went away and it ran better, but still slightly rough, like when I took it into ford. Drove it for a week and then the check engine light came back on (misfire cyl#7), and ran noticeably rough. I changed the coil pack on cylinder #7, the check engine light went away and ran better but still slightly rough. A week later the check engine light came back on (misfire cyl #7), and ran noticeably rough again.

The truck is now at the dealer, it failed a compression test on cylinder #7. They checked the injection system to see if the injector stayed open and washed out the cylinder, but that came up good. They ran a scope, but couldn't see any signs of a problem. They believe that the problem is in the bottom end and next step is to start tearing apart the engine. As I'm out of warranty, I'm afraid of racking up a huge bill tearing the engine apart and coming up empty handed.

Has anyone experienced this? Or have any ideas? It seems to me if it's an issue with the bottom end it wouldn't be intermittent? Basically it runs rough for 2 days with a check engine light, then runs good for a week with no check engine light, then repeats (this is on a hour long drive twice a day).

Andy13186

I had a misfire on my 5.0 mustang GT that ended up being the crank position sensor

dan02gt

It's probably the piston. Some of the early 5.0s (2011 & 12) had issues with the piston failing in #8. This was mainly attributed to overly aggressive aftermarket tunes. I know yours is a 13 and #7 but do a google search for "5.0 failed #8 cylinder" and you'll fine tons of info.

cjcnomor4

Have seen a few with valve issues. A cylinder leakdown test will probably have an air leak from the exhaust valve.

Zeegs

Just thought I would update this.

I did a cylinder leakdown test, and as cjcnomor4 stated, the problem ended up being leaky / burnt exhaust valves in cylinder 7. The head was replaced and Ford graciously covered a large portion of the repair.

Thanks for your help!

Headgoose

I have a similar issue with a 2012 F-150 5.0. 112,000 miles. Started to run rough. Took to dealer and they said spring issues with #7 an#8 cylinders. They bore scoped cylinders and said there was some scoring. To just fix spring and valve issue the cost is $6100 (only a band-id they say????)100. I am not a mechanic but worked on many in my younger days when I could not afford a mechanic. My question is -- Does this even seem reasonable? Just want a normal running truck. It was running OK - just the miss. Now it is in the dealers' shop and according to them these are my only options. I am no expert just been a Ford lover for years but now???? I need help from experts on this forum PLEASE! Thank you in advance for you time.

Headgoose

To add to my prior post the second option was an $8,100 new motor.

5.0nly

What's the odometer? I know in some other cases manufacturers will warranty it if it's just over the allowed mileage. But this is Ford.. they will do anything to deny a claim.

Headgoose

Odometer reading at 112,000.