I just recently replaced all 8 plugs and coils on my 06 f150 5.4L work truck at over 100K miles. It just recently had a bad miss that would kick going down the road, would idle rough and have the annoying ticking sound. So after replacing those and nothing improved, we were listening under the hood and I hear a random squeaking or chirping noise. Sounds like a bird is chirping and will change with engine rpm's. From what I can hear, it also sounds like it is coming from the first cylinder closest to the front on the passengers side. This was probably occuring before and has just got worse over time, but since I can only really hear it with the hood open, I had not noticed it. Im beginning to think that I either have a bad injector or we possible have a bad coil? Im not really sure, but If anyone has had a similar issue or has any suggestions it would be greatly appreciated. Thanks

 

Does it still have the miss you say it just recently had a miss and you changed the plugs, that didnt fix the missfire? sounds like its in the valve train. Cam phasers or loose tensioner A bad injector or coil wouldnt make a noise it would just missfire

 

Yea it still has the miss. Something else I noticed was when Im going about 55-65 down the road and I give it alot of gas, the truck seems to run better. It only really struggles when it gets to lower rpm's, either at idle or when the TC locks and the engine gets down to lower rpm's.

 

passengers side rear spark plug was loose. replaced it and snugged it up. now the truck runs like new.