Is it at all RPMs?


Harmonic balancer bolt loose? My F150 did that and the bolt was loose. Tightened it up checked the timing and drove her. Somehow my brother had loosened it while helping me out.


Any metal or anything like that on the dipstick?
Oil still look good on the dipstick?


How is the oil pressure? My 88 F150 had a rod throw it was running great then next thing I know rod started knocking sounded up high then I knew what happened when it finally went.


OL' navy I have switched oil brands before and never had a problem with it except when I move from regular to synthetic oil it blew up a motor.
Trav

 

I cleaned out the EGR valve, oil is clean no metal shavings or anything in it, and it only happens at low RPMS. Over 2k there is no knock present

 

Is it possibly coming from your transmission. I know on low RPMS my dad's 89 F250 4x4 351W ZF5 stick shift it makes a knocking noise and it sounds like from the engine but it is really the trans which from what I read is very common. Haven't figure out what causes it though.
Trav

 

Yeah I've heard the ZF5s are noisy but my trucks an auto

 

Hmm this is fairly weird. Maybe does your dizzy have slop to it causing it to rattle and make a knocking noise. I have heard of it but only once.


I would do the paper clip method and pull codes unless you have an OBDI code reader.




Being that it is only at low RPMs I wouldn't think it is a rod about to go or anything like that because I would think it would get louder at higher RPMs.
Do you have any CELs?


I am kinda going out on a limb right now as my dad has never heard of anything like this and I can't think of anything any more.


What I would do is just double check everything that everybody else has said just to be 100% sure. It isn't going to hurt you or your truck to check it (at least I don't see any reason.) I can't count the number of times I said that it wasn't that and it ended up being that.
Trav

 

Thanks for the advice. Haven't tried to pull any codes yet maybe I should. Going to change the fuel filter, and repair some vacuum lines that have leaks and I guess I'll go from there. I really don't think it's anything serious because the timing changes the way it knocks drastically so I'm leaning more towards a detonation issue. Also the thing runs amazing aside from this knock.

 

Always pull codes. It's the simplest most informative test. Try to locate the sound. Use a stethoscope or piece of hose. Try eliminating cylinders by disconnecting spark plugs and fuel injectors. If the sound goes away you found the culprit. Check the flange to down pipe joint on the exhaust. Its a common leak especially after work and sounds like an engine knock.

 

Flange is tight on the down pipe and I know it's not coming from there, noise seems to be coming from the upper part of the engine. Definitely going to check codes, only reason I didn't first off was because I didn't even think with OBD1 they threw any codes. Guess you learn something new everyday!

 

Yep they sure do throw codes.... Hundreds that can be thrown they're actually quite sophisticated

 

Hopefully I can pull something that'll help me solve this issue. Keeping my fingers crossed