New Noise from Engine

Man it doesnt stop.

Anyway, plug wires are on correctly but I still have a rough idle. I am going to buy a dwell meter when I can to make sure the points are as dead on as I can get them. But now when I give it gas I hear a noise that I can only describe as a piston slapping or something. It has kinda the sound a deisel engine makes. Could this result from a dead cylinder or what?

 

lifter sticking? or my favorite, exhaust heat riser flapping?

 

Hope this isn't it, but a loud bang-bang-bang is most commonly a rod bearing. What's your oil pressure?

 

It's not a loud bang bang at all. It's not really loud but it's easily noticeable and only happens at lower RPM's while applying gas and fades away once the engine gets higher in the power band.

 

you might consider a quart of marvel mystery oil substituted for a quart of motor oil in your next oil change? I think it helps some with lifter noise. that is a common ailment in our old :v6: 's

 

To find a dead cylinder with engine running and using insulated pliers pull sparkplug wire one at a time, if sound/idle changes that cylinder is good, if it is unchanged it's a dead cylinder.

 

Could it be detonation/knocking from the ignition being too far advanced? That is a diesel sound for sure.

Also caused by high compression, or low octane.

Especially under acceleration or load.

Pete

 

25-30 Does that sound ok?

 

At what speed? If that's when the oil is hot and the engine is idling, it would be ok <edit> not just ok - good. Rough rule of thumb, you need about 10 psi per thousand rpm, although 7-8 psi at idle is worrisome.

 

It's around that when I am just cruising at normal speed. I dont have a tach so I am not sure exactly.

 

get a long screw driver or pipe or something (stethascope maybe) and lay under the engine. place it on your jawbone by your ear and probe the block around where the pistons are. have someone rev it up as you check in difference spots. might help isolate piston slap from rod knock if you think its mechanical. its an easy check without disassembling anything. might help rule out lower end if you dont hear anything. how sound waves propagate down a dense medium fascinates me, and can tell you alot.

 

I had that same knocking sound a couple years ago... It wasn't good. The crank was wayyy out of wack. I had to remove it and get it turned down.
Your symptoms were exactly the same as mine. The diesel sound would be louder when the engine is under pressure.

Hopefully, it's not this and something stupid. But, at the worst case, it's a new turn of the crank.

 

Yeah oil looks good. I am noticing this less and less when I drive. I slacked this weekend on getting anything on the jeep done. It'll be warmer next weekend and I'll get around to looking a little deeper into this and some other minor things.