I just recently purchased a 2010 f150 with the 5.4 v8 with 111000 miles. I drove it for about 250 miles with no problems. Then one day I noticed a stutter/hesitation at start up when accelerating. It mainly occurs when it is cold then goes away for the most part once it warms up. Then I got a Code p0307 which is for a cylinder 7 misfire. Took it to dealer and they replaced coil and gave it a new set of spark plugs. The next day it still had the stutter but didn't throw a code until a few days later. Same code p0307. I took it back to the dealer and they checked the intake, injector, coil, and plugs again. All checked out ok. They kept it a few days and said it lost some coolant overnight and they think coolant was leaking into the cylinder causing the misfire. So they thought it had to be the head gasket, head, or crack in the block. They did a compression test and it was fine. They gave me the truck back today and said they basically don't know what is causing the misfire and told me to just drive it unless the stuttering gets worse. My question is what could be causing the misfire? Any advice would be greatly appreciated.

 

Take it to a different dealer or a GOOD independent shop.

A compression test is only one way to check for a leaky head gasket or cracked head/block. Have a hydrocarbon test done on the coolant, and a cylinder leakdown test may tell you something. Borescoping the cylinder may reveal something.

 

Will do glc, thanks for the advice.

 

Update: I took my truck to a very reputable local mechanic for a second opinion and they pretty much came to the same conclusion the dealer did. They checked everything external and said it has to be something internal. They said they have seen a lot of problems with this engine due to its design and cam problems. They do not know what is causing the code and misfire but said it is something internal. They said a new jasper engine is between 7-8k but did not recommend getting it replaced because basically it is not a good engine design which I do not believe. They suggested I just trade it in for another truck other than a ford. I am not sure where to go from here. I've taken it to two reputable places and both said basically I have a major engine issue. I just bought this truck after looking for several months and hate to get rid of it for a big loss. I also hate to have to put a new engine in since I am not sure what exactly the problem is. I don't want to have to take it and pay the labor to diagnose it from yet another mechanic. I am really torn as to what to do and would appreciate any advice. Thanks in advance for the help.

 

I have a similar problem. 2005 f150 5.4l

I got lean codes and 7 misfire codes, so i replaced the intake manifold gaskets, injector seals.

Still misfiring, but wouldn't throw a code for about 20 miles. Then it started backfiring and gave a cylinder 7 misfire code. So i switched #7 coil pack to cylinder 6 and the misfire moved to cylinder 6. So i replaced that coil pack.


The backfiring goes away, but after another 20 to 30 miles, cylinder 7 misfire comes back, then cylinder 8.

Spark plugs were replaced by the dealer 10k miles ago. Fuel pressure is good, no injector faults, all o2 sensors working, map sensor is good, also replaced an old vacuum line.

 

There was a recall on the injectors in the 2005 MY. If you have not yet replaced the injectors suspect them.