Knocking Sound When Idling in Gear

So for about a year now I've been hearing a knocking sound while in drive but stopped at a light or stop sign. It seems to happen about once per revolution and will speed up when I start to accelerate but will get quieter until about 2000 RPM and then can't be heard. If I put it into neutral the noise basically disappears or gets much quieter. It only seems to happen after the truck has been running for about 5 mins then goes away after about 5-10 mins or once the engine is fully warmed. The outside temperature doesn't seem to have much affect on it other than making it take longer to go away.

I can hear it best from inside the cab and under the dash. I've tried listening under the hood while its happening but couldn't hear it over the engine noise.

I've had my local stealership "take a look" but they figured it was a wire from my HID's rattling around lol. Obviously that is not the cause. I originally thought piston slap but shouldn't that go away once the engine starts warming up? Rather than START happening once the engine warms up a bit.

2013 TRD Sport with 50k KM. Factory drivetrain. 4.0 V6 auto.

Update March 30: Just had the noise happen again. Quickly popped the hood and removed the intake tube. Can confirm this is NOT the cause of the sound. It sounds like it's coming from the engine itself. But can not be heard from the engine bay over the other engine sounds. Which makes me think it is internal and the vibrations are carrying into the cab. I originally thought piston slap but it sometimes happens well after the engine is warm like in the video...

Here's a video. https://youtu.be/uFJx75kTmEw

 

Not regular enough to be engine. The sound has differing ocsillations.

Trans fluid low? Once it expands from temp rise makes the sound go away?

 

Hard to say... Could be possible. It drives and shifts perfectly fine even when making this sound. I've never checked the fluid level but after reading about what checking entails, I may just be leaving it that way lol. I still have warranty but if I tell the crooks at my local dealership to check and that isn't the problem I get charged $135/hour shop time. I'm trying to see if there is any way of narrowing it down before hand.

 

I would have that level checked. There was a rash of Tacomas from '09 to 15' that were under filled. At least for peace of mind.

 

Saskabush...I know you responded in attached thread...have you checked the intake snorkel to fender for damaged gasket or foam. Sounds similar to what I had. Sound is worse down by pedals.

https://www.tacomaworld.com/threads/thumping-noise-at-low-revs-under-load.480557/

 

That does sound similar for sure. But it must be something different on mine. That foam gasket is in excellent condition still and has lots of play left. I just check that this weekend to make sure. Thanks tho!

 

Update: This weekend I took a good luck at everything I could. All motor/tranny mounts look new still, intake tube gasket looks perfectly fine, doesn't seem to be anything that could be rattling or vibrating on the exterior of the engine.

Still searching... Any feedback or suggestions are appreciated!

 

Inspect the sound from the exterior as it is doing it. That will be the only wah you could find it. As far as guessing goes, for us on the net, it's a toss up. It could be ANYTHING. It definitely is not going to be the engine though, that's what I can tell you.

 

I had a knocking under my hood yet the truck runs excellent. Couldn't figure out what it was for the longest time. The problem ended up being the casing around my cold air intake. The weld had broken and the air filter was rattling against the housing of the air filter.

Rewelded the piece; rattle is absent.

Worth looking at if you have something similar under your hood.

Cheers,
-P

 

yeah you are going to have to get out and inspect it when its doing it. (have someone you trust hold the breaks with it in gear for you as that sounds like when its doing it)

Maybe a heat shield on the exhaust?

 

The gasket on my intake tube looked fine also but was the source of my problem. Could not tell where or what was making contact. Also could not hear the noise in engine bay or outside vehicle. Could only hear it from the driver seat... down low by pedals.

Disconnect the tube from the intake and take it for a ride and see if noise goes away. Im almost positive its what your problem is. I chased this problem for years and couldnt believe it myself when I finally found the source as suggested here on TW.

 

That is pretty much exactly what is happening to mine. There was one time I tried popping the hood while it was happening and had a listen (had to put the e-brake on and leave it in gear ) but I couldn't hear it at all from the engine bay.

My problem is intermittent so removing the tube won't really tell me anything unless I leave it off for like a month. I wish it would happen every time! It would be way easier to diagnose. Next time I hear it I'll try to play around with that tube though and see if it helps. That would be great if this was the problem!

 

I have tried to get out and see if I can hear it from under the hood. No luck unfortunately. I had to just put the e-brake on and leave it in gear. Whatever it is is completely masked by the other engine sounds. I also checked the heat shields this weekend and they don't rattle at all. It doesn't really sound like a rattle at all actually. It sounds like someone is tapping their knuckle on my firewall.

 

Saskabush...Ive tried more than once to convince you to just take the damm thing off for a while and see if its the source of your problem. Only takes 3 minutes tops. My last post on this subject.

 

Loose baffle in the cat ?

 

Removing it right now tells me nothing. I'd rather it make the noise so I can verify what it is than start removing things and never know what is actually causing it. I'm going to leave it alone until I hear the noise again and that will be the first thing I check to see if that is the cause or not. It's easy enough to check on the fly. I carry tools in my truck and can quickly remove it if need be once I hear the noise again. That cool with you??

 

had this problem with mine. it was the intake tube on the inner fender. when I put on my trd intake noise went away.

 

Just had the noise happen and quickly removed the intake tube... Didn't make a difference unfortunately. I was really hoping this was the cause because it's a lot easier to fix than something internal! Thanks for the suggestions.

 

Damm...I hate being wrong. Hope you get it figured out!

 

You ever figure this out? My 2012 doing same thing exactly.