I have a 2004 F-150 with the 3 valve heads. Recently, my truck had a missing/backfiring and sounded like a dropped valve hitting the piston. The noise stopped after a couple seconds then had the exact same problem about 30 seconds later. I immediately shut the truck off to prevent any further damage. I have tore into the engine and after getting the heads off, have found no problems with the valves or any marks or indication that the valves have hit the pistons. I have been turning wrenches for over 10 years, but have not dealt with these engines any except for a doing an engine swap for a customer due to a dropped valve that cracked the piston and block. PLEASE HELP!!!!

 

Sounds like you may have a lash adjuster that went soft and allowed the follower to bounce around or even come off that could give you the noise and missing condition you had as well. Did you inspect the lash adjusters and followers to make sure they are all secure and tight with no movement? Was the timing chain tight before you removed it? Any broken sparkplugs or small dents, dimples on the piston dome? There were things that you could check before removing the heads. Not sure that was nesessary. Next check the suspect head valve train (followers, lash adjusters) real good including the VCT.

 

I checked the timing chain... both seemed plenty tight, even with truck not being started a week prior to working on it. Did not notice what seemed like excessive play in the followers that didn't have pressure against them. And the plugs were good, and no dents or marks showed up on the pistons or heads.

 

Well if you can't find anything wrong you may have had a bad miss. I suspect there are no codes. If the valve train is intact and nothing shows any damage you have a delema. You may have to put it all back together and run it to find root cause of the problem. The absolute last resort is to tear the engine down without first identifying the source of the condition. Making an assumtion that you had the same problem as the engine you pulled on a customers car may have made a lot more work for you then necessary. I don't mean to sound like a jerk but always perform some diagnostics first. A visual of the valve train, if all looks good then perform a leakdown and compression test. Pull the plugs and find someone with a borescope you can use to view into the cyl bores looking for piston dome damage or debris in bore without having to remove the cyl heads. I could be wrong but I don't think the heads should have been removed. Right now while its apart go over everything with a fine tooth comb. Look for anything that could be broken, bent, loose etc. If you feel confident nothing is wrong then your only option is to reassemble it and determine what really happened. If you have questions on something get back with us. Not sure if something is normal take a picture and send it, everyone here will do what we can to help you. Good luck