I have a 1995 ford f150 with the 300 straight six that is making a slapping kinda clicking noise through all rpm's but it doesn't do it all the time sometimes when its hot sometimes when its cold I thought it was a spark plug that was kind of loose and the porcelain was moving around on then I replaced that and it still does it any thoughts? thanks

 

Well if it's not upper (rockers, valves) it could be a broken piston skirt or rings. That usually doesn't do the intermittent thing you describe. Back in my twenties I bought a mechanics stethoscope. Used it countless times and it has helped pinpoint stuff. What I would do is while it is making the noise , try pulling plug wires (I use insulated pliers and a thick dry welding glove) one at a time then plug it back on. See if it changes if any one cylinder is killed.. Another thing that it might be is an exhaust leak, especially around the pipe. Makes kind of a clapping noise. Just guesses or course.

 

thank you for the input! Turned out being quite helpful

 

So what was it? Don't keep me hangin'.

 

Dont you just hate that .

 

Lurker here... This drive me BONKERS!