J

I've had this for a long time on my 4Runner, but it's always bothered me and now i'm getting somehwhat worried about it.

When the truck is started cold, it doesn't do it.
When the truck is warm/hot, it doesn't do it.

It only seems to happen when the truck has been hot and then left to cool, say for an hour or so, and then started again. When i give it a little gas (to around 1200-1500rpm) i get a knocking sound from what sounds like ONE piston. I can't verify it's a piston or not, but it sounds heavier than a valve. It is NOT a pinging, or knocking or anything related to early ignition or detonation. It is regular (like every revolution) and varies with engine speed obviously. It honestly sounds like a piston running without any lubrication or something. However, if I just give it some more gas and above 1500rpm, things become very smooth and you don't hear a thing! After a short while, when the engine warms up again, it no longer does this...

I JUST changed the spark plugs about a week ago and they were ALL in very good condition. Worn, but not oil fouled or burned.
Idle is good, acceleration is good, and it's done this for a while. It sounds bad when it's happening so taht's what makes me worry. It's just strange that it goes away.

Anything i can do to narrow down the possibilities?

Thanks,

Jason

rimpainter.com

Have it compression tested, that's one idea.

PY

Get a stethiscope if you don't have one and use it. It will help you identify the source of noise very quickly.

Does it happen in neutral or only in gear? Could it be the fan clutch (assuming you're not using an electric)?

J

Yeah, didn't think about that....
Sure idles aweful nice to have compression problems though. You would expect a shimmy or something at a standstill if it were low on one cylinder.

I have NOT checked to see whether or not it does it in drive or in neutral. Will check tomorrow!

Thanks for the ideas...

Jason

rchavis

Mine does this too and my compression test are good@175. Dealer was unable to find a problem. Took it to another mechanic. Could not tell what the cause was. He did say that these engines do seem to do so unexplain noises some time. He has a Toyota truck with the 3.0 and he says his will make this noise sometimes. But it is annoying and now that you've brought it up, I would like to get to the bottom of this before it's too late.

J

Small edit and update...

The knocking sound occurs right around 1100-1200 rpm, and goes away quickly as the engine gets above that.

Also seems to do it when fairly hot too, so i take back my statement above that says it doesn't do it when hot. I will do more experiments when i get time to sit still and give it a little gas to listen...

Jason

descendents

hows you oil pressure?? this could be from low oil and oil pressure. better check that soon/first

kelly

J

Oil pressure is good.... I've kept an eye on it and it stays well within the 'acceptable' range.

Jason

J

More updates:

It doesn't seem to make the noise at all when cold. Obviously the engine is a "little bit" louder when cold anyway but you definitely don't hear the noise.

Also, the noise isn't really a knocking like i've said....only somewhat.
It is not just sharp and abrupt like a hammer or something hitting a hard surface over and over. It's more like a really short, repetitive grinding sound with a knock all at the same time. Hard to describe....obviously.

Thanks as always.

Jason

descendents

have you checked oil level as well as pressure? gotta do these little things first... if it is low oil this could mean $$$$

kelly

Tragic Drive

Sure enough my 89 3VZE will occassionally make this sound. However its been doing it for over 80k miles I now have 140K on the motor. I did the compression check and it was better than toyo's specs. Small bit of info but possibly useful is that the sound went away after I cleaned the engine ( prolly coincidental ) and changed the oil. In any event I havnt heard the sound in a few K miles.
Yeah I know, sounds like BS but this is from my expierence. I really hated that Knocking sound but nobody else noticed it but me.

J

No, the oil level is just fine...

I did some more testing today while at a standstill and it seems to be only noticibile when IN GEAR. If the truck is in Drive or Reverse and you give it a little gas, the sound is pretty distinct.

I have sort of narrowed it down to something slightly BEHIND the engine. Possibly the torque converter, i'm not sure. I had decent clothes on when i was testing this or i would have gotten under and pinpointed it. Next time, i'll find a buddy, have him step on the gas, and i'll get under it and try and find the source more accurately. I'm still kinda just guessing.

I'm not going to worry about it until i can have a more accurate position of the noise source, i'ts been doing this probably ever since i've had the truck.

Jason

CMUpike

My truck's been doing the same thing too. Only it starts knocking (ticking, clanking) however you want to describe the noise, when it's idle. However, the engine has to be warmed up in order for the noise to start. It's also strange that as soon as it makes the noise, if i kill the engine, and fire it up again, the noise is gone. The noise also is louder when i switch from drive, to park, or to reverse. but just for about a full second when it's switching gears.

I have noticed that the noise is no longer as loud as it used to be when i lived in pittsburgh. I'm not about to believe that something like this "fixed" itself, but there's not really a whole lot i can do. My dad thinks that I should just drive the truck until it dies on the side of the road. My only other option is what my mechanic said to do, and wait until the noise is REALLY bad, and he can take it apart and send it out to an engine rebuilding shop. The latter choice would be much cheaper and perhaps more reliable than buying a junked engine. He also stated that the engine shop can polish all the ports and make everything really nice, so that it "should" perform better than buying a new engine... which i would assume would cost a fortune.

anyways, i feel your pain man. If anything happens, i'll be sure to let everyone know what choice i'll make. until then, i guess i'll have to keep on truckin'

CMUpike

oh, i forgot to add, my mechanic used his stethoscope to try and pinpoint where the noise is comming from. he claims that it is MOST LIKELY the main bearing not sitting properly, or the crankshaft is somehow warped and hitting against the longbody.
(or something of that nature, I have a terrible case of ADD and my mind wandered off while he was talking) The first one he said is more likely since he's seen a few cases of it happening before. The reason why he told me to wait until the noise is really bad, is because he can't really tell exactly what is wrong, until he disassembles the engine. Since that'll be fairly costly, he didn't want me to prematurely open everything up, especially when my truck would be out of commission for a while.

i hope some of this information helps.

CMUpike

just an update to the subject....

I just changed my oil yesterday, and switched to 10W30. i was generally getting the cheap, 5W30 oils. The 10W30 was the same price, and the noise has stopped!

this is remarkable, since this noise has been going on since the 4runner get together at Dave and Busters (white flint mall, MD) this past christmas.

now, i'm not that stupid... i know the problem still exists, but if the sound has stopped, which i assume means less wear and tear as the noise came from something rubbing or hitting.

so perhaps a temporary fix for your problem may be to use a heavier oil?? just a thought.


cheers

ewarnerusa

I have had a knock in my '01 tacoma 4 cyl for a while now, but it sounds like mine may be different since it is basically whenever I have a cold start. it goes away when the engine warms up. But really for the most part it sounds like your same issue. I have taken it to a mechanic and he said similar things to what rchavis's mechanic said. I have read this site, http://www.canadiandriver.com/articles/jk/020320.htm, which seems to explain things. I will try the 10W40 oil next time, because I think I've been using the 5W30 all along, too.
Ed

J

Ok, just a few more tidbits to add:

About the oil...
I have run Mobil1 Synthetic 10w30 in my truck for the past couple years. I have recently (yesterday) put in Castrol Syntec just for a test.

So, i've been using 10w30 for a long time. I considered going thicker, but didn't want to. I really don't think that's the problem. If i were using the 5w30 then i would go up, but i think 10w30 is thick enough.

Also, by having a friend put his foot on the gas and me putting my head under the truck, it seems like the noise is low, and possibly toward the rear of the engine. I almost thought it was the torque converter or maybe the front of the transmission, i can't tell though. I need to get under it with a good ear and listen.

I have heard the noise when the truck was in neutral, but very faint compared to what it can be. The times it is worst is when it has been quite hot, and then cooled down for an hour or two. It's quite worrying at those times, but goes away quickly after a short drive.

What baffles me is that the noise COMPLETELY goes away as the engine revs past about 1500. I mean GONE. If i give the engine a good amount of gas off the line, i never hear this noise. Only at low rpm (900-1400) under stress (connected to transmission) does it ever do this.

Any more help is appreciated.

Jason

CMUpike

well, it was working for a while, but the noise has come back!!! i'm pretty disappointed, because i was pretty excited that it went away. Well, it just goes to show that problems don't just "go away".

jason, it's the same thing with me, when i start driving, the noise goes away. sometimes, if i take a sharp turn at low speeds, i can hear the noise too.

it sucks, because i can't really fix it right now, because i'm unemployed and i don't have any money. however, if and when i get a job, i'll try to get it fixed... when that time comes, i'll let you all know how it goes.

J

NEW INFORMATION:

I've narrowed mine down to a definite piston/cylinder problem.
Tonight, while doing some other work on the truck, i did the following:

I would rev the engine just a bit from the throttle body, and i could hear the noise. I took a plug wire from off the distributor one by one and revved the engine after each one.

It turns out that when I disconnected Plug 1, the noise went almost completely away! So this tells me that it is NOT a valve, or tranny or anything else but something in that cylinder.

Is it possible to have oil starvation in a single cylinder? I don't know anything about lubrication and how the oil is transported around in an engine so that may be a stupid question, but can someone help out... What would cause a single cylinder to make that knocking/grinding noise when warm/hot?

Any help is great!

Jason

Jay

By pulling the plug wire for a specific cylinder you have releaved that cylinder of the forces of combustion. Thus eliminating the stress on that cylinder.

That is a common test when diagnosing "lower end" noise. I regretfully inform you that you indeed may have a serious noise. The possibilities are few, a) Excessive connecting rod bearing clearance b) Loose / Worn wrist pin c) Collapsed piston skirts. All of which requires engine removal and usually machine work to correct properly.