hello all.new here and been searching the forms for some awnsers to my trouble.
lots of causes i have seen here seem like they could be whats wrong with my truck.
so i figured i should just ask.

i got an 08 with the 5.4 flex fuel with 93k. up untill i changed my oil last week it has been mint. I did go about 5k on the oil. As soon as i changed it though when truck is up to temp and either at idle or i slightly rev to 1k rpm or so and let off. The engine will start to knock badly and try to stall. I hit the gas and bring the rpms up an its just fine. Now my problem is this. Threw my diag of the cause i have found if i unplug the vct solenoids the issue is gone.So started replaceing the vct solenoids and found that on the pass side the timeing chain on the top side of the cam or the top chain guid has alot of slack. almost to where i could just pull the chain off.the drivers side is not like that it's set right aginst the guid with no play.So im guessing the top guid must be broken but i can not see it as i only moved the valve covers enuff to get the vct's out. I also noticed the new vct's are updated.Im a honda tech an we replace the vct's on newer 4cyl due to this an that.and the same changes to the solenoid where made.so i still wounder if its the vct but suspect the guid.i will get a inspection camera an see if the guids broken.but tell then im stumped. Thanks to all for any input
Also I am awear of the phasers.but with the chain slack and the updated vct I am not ready to go for the phasers. I am working on my truck during lunch so I only get to put in and hour or so on it so I am trying to avoid pulling the timing covers an less it's a likely route.

 

That slack in the timing chain you talk about could be the cause of your knock. If the guide happens to not be broken, you may have a collapsed timing chain tensioner or blown out tensioner seal, or both.