Knocking sound, help me diagnose

[Zenja]

The sound is most apparent in 5th gear at about 30-40mph, but also easily heard in 4th gear at 25-30mph. While keeping steady speed or decellarating, if I give it some gas (even a little bit is enough), it sounds like the engine is knocking very loudly for a little less than half a second, and then it goes away. After that I get massive vibrations throughout the car.

It sounds like the way people describe knock: the sound of something rattling in a tin can. There's a ping with each engine rev (sounds a little like lifter tick actually), and also a constant, general hollow metallic sound. It seems like it's coming from the engine bay. I can pretty much recreate the sound by free reving in neutral while stopped, putting my ear by the air filter and giving it gas. Once I hit the gas, I hear the same sound through the intake. I almost imagine it as the sound of injectors squirting.

I have a feeling this is related to the huge knock that I sometimes get on my logger at low throttle and low RPM. I haven't checked yet if the sound directly corresponds to the knock on the logger.

I've heard the sound through the intake before, but only noticed it while driving tonight and it scares me. I hope it's not massive, real knock. I'll look into it some more tomorrow. Does anyone know what it might be?

 

[grizzly]

this is called lugging the engine you are putting a huge load on the motor cause basically 4th and 5th are overdrive. you can hear it in 3rd too if at a low speed. but yea you are lugging the engine. it can cause spun brearings knock you name it.

 

[Zenja]

I know it's lugging a bit but I'm only giving it slight gas. Also the sound goes away about half a second after giving it gas, and after that there's the regular lugging feel.

 

[Spoolin4Ever]

We're skeptical because you are lugging it so bad. No other weird sounds when driving it in appropriate gears and engine speeds? It could be normal then...

I am not sure if mine does it, because I rarely lug it THAT much. I mean that is extreme lugging.

If you are truly concerned, record it with a hand held tape recorder, get the recording in MP3 format, and post it up.

 

[Zenja]

Yeah, my next step will be to get it on video/sound. It sounds like there might be a similar sound (no ticking, but still the hollow metallic sound) at higher RPMs and higher speeds (ie 5th gear at 65mph up a slight hill). Anything else I can't really hear because the car is loud right now.

I know that the situations I described sound like a lot of lugging, but I don't really have to lug it more than a slight amount to get it to reproduce the sound. Also, it seems to not happen 100% of the time because I was trying to show my friend the sound today and it didn't really recreate it in the same way.

The strangest thing that stands out to me is that the sound only lasts for the first half a second or so even if I continue to hold the throttle at the same level after. I guess I should also mention that the sound could be due to driveline play (which I have quite a bit of due to the rear diff) or the driveshaft smacking under the car, but it really sounds like this sound is coming from the engine bay.

I should also restate that I can hear quite a similar sound in the same duration and circumstances while just stopped with the car idling and in neutral. If I open up the throttle body, I can hear something loud and clear coming out the intake.

Thank you.

and your not using your lower gears because their broken ? like your motor ?

.. What kind of post was that?

The lower gears work fine. The point is that the sound is most easily heard in higher gears (more load), which helps people diagnose it. I've been having some weird problems and I think this might be related, and if nothing else then it's a sound that shouldn't be there. I haven't heard it on any other car.

 

[grizzly]

any lugging is bad. no questions and going up hill you should down shift cause like you said more load = lower lugging speed. like shifting into a higer gear b4 you actually should more load.