Strange Knock just started, please advise

Hey Guys,

I'm worried about a knock that I just noticed in the last week. It's coming from the driver side, seems to be top of motor but I can't tell for sure. I have had this 96 tacoma 3.4L for about 9 months. The previous owner said he ran synthetic and I run Mobile 1 5w30 with a M1 filter. The oil is super clean. I'm hoping this could be something other than a serious knock but need some advice. I have attached a video. Thanks for the help

 

with the engine running do you hear it on the bottom end? You'd probably be best to use a stethoscope or long handled screwdriver to try to listen to the noise and determine where it's coming from. (ear on screwdriver technique). Sounds a bit like a bearing of some sort.

 

Sounds almost like a loose lifter... I'd recommend having it checked as soon as possible...

 

Kinda sounds like a spun rod bearing. Like scotrinaf said have it checked asap.

 

Doesn't seem to be a spun rod bearing. My bro spun a rod bearing in his truck, and it knocked HARD and engin would not run. I only know what a spun bearing sounds like, but I would deff have it checked though.

 

Definitely sounds like it could be something VERY BAD to me.

 

Dude .... thats a rod knock

wasn;t sure till you revved it up, sure sounds like one to me anyway

 

Thanks for the replies guys. I figured out what it was today. I took uberjason's advice and used a screwdriver to try and narrow it down. (thanks for the tip dude, hadn't heard that before). Anyway, as i used the screwdriver I couldn't hear the knock internally so I started looking and listening and narrowed it down to the driver side valve cover. Turns out the #2 plug had turned (Loosened) almost all the way out and pushed the wire boot off it's seat. The noise was actually the compression coming out the spark plug hole. I tightened the plug back up and seated the boot and noise is gone. Thank goodness, I was a little nervous on this one. The reason I bought a Tacoma to avoid major problems. I've never had a plug do that on a vehicle so it was kinda strange. I'll keep my eye on it and make sure it doesn't loosen back up.

 

i had that happen on my old 96 once after doing plugs,oddly on the drivers side as well.

 

Weird, I think it has happened to me on motorcycles but never on one of my trucks.

 

Where are you at? Wonder if its my old 96? LoL

 

Well gotta say it sure doesn't sound like escaping compression to me & if the plug was loose & the plug wire was loose /off the plug, wheres the cylinder miss ? That motor should've been shaking & shuddering with even 1 misfire, but if you say thats what it is, so be it

 

That's great news. I was kinda worried it would be a rod knock too. I've never heard anything quite like that so I wasn't sure what it is. It sounded kinda like a rod knock to me except the sound is much more hollow, not quite as low, and no double taps.

 

Similar thing just happened to my 2000 4Runner. One night it was making a ticking noise (like a valvetrain noise), and the next day it shot the #3 spark plug out of the head, and took all the threads with it. The machine shop was able to heli-coil the spark plug hole, but you're lucky you caught that when you did.

 

Dude that's why I was so surprised. There was no misfire at all. The motor was running when I narrowed it to that plug cap. I pushed down on the cap and seated it back on the valve cover while it was running. As soon as I did that it sealed up and the noise was gone. It was probably only like an 1/8" off it's seat. I'm not positive, but the plug was probably about 3/4 the way out. Could have been less i guess but it was enough that air was getting by it. I'm just glad I caught it before it went any further and blew the plug, and threads, all the way out.