so this is the timing chain on the passenger side of my F150 4.6. My question is, is the slack it has in the picture ok? Or could it be contributing to my issue with a cylinder 1 misfire? If you pull up and down on it, it flops up and down like hella crazy. I had a noise it was making around there and I wonder if this is what it was. The other chains have very little slack at all or none at all. This one is like sagging almost into the other chain and I know it has to be flopping around in there. I can almost take it off by hand. Surely this can't be normal.

 

You replace your chain tensioner on the passenger side? From what I've read, that's the one that usually goes, which creates the slack, which creates all the issues - broken chain guides, loose chain, depriving the passenger top lash adjusters the required oil etc....

I fear to have the same problem as all old 5.4's seem to get with miles and age. I'm sure there are exceptions,

 

I think you have already answered you own question. I assume that you have some miles on the engine to be dealing with this. IMO while you are already
in there do the chains, tensioners & guides. These modular motors are kind of fickle about that. These motors are rumored to have a life of
upwards of 300K IF you maintain them on schedule & replace the hardware above every 100K. Anyway I wouldn't take that chance, the replacement guides
& the tensioners now days are a better design than the original.

 

Definitely! This engine has 217K and it's the original chain 😳

 

Well I'd say you got your money's worth. Next question is, since you may have about another 100K ish left to go, is it better to
repair it with new parts or forgo the 100K miles & replace the engine now? Depends on whether your going to keep the truck or not.

 

I'm going to repair it. I'll continue to repair the engine until it absolutely cannot anymore lol

 

Give it the care it needs & it'll serve you well.