Who has thump/knock while idling in gear?

[COShadow]

There are other threads on this issue. I have a thump/knock while in gear after the truck has been fully warmed up and driven a while. The noise goes away in P or N. Dealership changed timing belt and "tightened things up" and this helped quiet the noise somewhat until I had the other drive belts changed-- now the noise is back and loud as ever (heard best from inside while while waiting at a llight.). The dealership said it's coming from the lower engine, possibly main bearings. ??

I have 160,000 miles and the noise has been around for quite some time-- I don't remember when I first noticed it. I've owned the truck since 92K and have maintained it well. The truck runs ok, with decent power.

I'm curious to know who else has this / how many people have this and what solution is out there, if any, short of getting a new engine. Is this a weakness in the 3.4L engine? I'm not sure I'd want to replace the engine with the same type if this is likely to happen again....

 

[jgue467]

Main bearings its probably not - that sounds like a hammer hitting something solid repeatedly and once it starts will not go away till the engine is destroyed.

The fz engine is probably one of toyo's best of the era, no inherent issue there. Most purr like a kitten.

Since you included no audio file its tough to tell..... :cowboy:

 

[SpidermanGeek]

Any vibration or just the sound?

 

[slimboiphat]

I have this as well. It's comes and goes but mostly during idle while waiting at a stop light. A very subtle knocking noise. Interested to know why this is. This hasn't given me any problem...yet.

 

[COShadow]

^^^ thanks 4 the reply. I'll try to get an audio recording of it. However, the people who have it will know what I'm talking about from the above description. Toyota mechanics are the ones who told me its probably the main bearing, but hey could be wrong.

^^i haven't noticed alot of vibration, just the noise.

^ From the reading I've done there are more than just a few people with this noise. It must be a component common to the timing belt and the other drive belts since they've both had an effect on the noise.

 

[LeeMajors]

I have something similar, but I only notice it when the RPMs dip down to 600 when idling in gear.

I wouldn't describe it as a knock, but like a glug (glug-glug-glug-glug), low frequency sound. It doesn't sound destructive or anything--no hard metal-on-metal, or grinding. The truck continues to idle smoothly.

My old 11 Tacoma 4cyl-manual had a similar noise when sitting in neutral with the clutch engaged. Who knows.

 

[SpidermanGeek]

Piston slap?

http://www.toyota-4runner.org/3rd-gen-t4rs/108334-knock-idle.html

 

[COShadow]

Piston slap?

http://www.toyota-4runner.org/3rd-gen-t4rs/108334-knock-idle.html

I don't think it's piston slap because it doesn't do it when the engine is cold but becomes audible after it's fully warmed up and has been drive for a while. Thanks for posting the link to that thread, it is one that I had read through previously- but no apparent answers there.