Knocking under light acceleration? Whats Happening!?

Hello all,

Ive been noticing a knocking sound under acceleration only during acceleration from 1100 to 1700 RPM.

This happens only when the engine is warm and happens at nearly any speed as long as I'm within the RPM range and accelerating.

Idle is smooth and higher RPMs are smooth. Any suggestions as to what may be causing this or is this considered normal as the engine ages.

Specs:
2009 4.0L V6 165k miles, 5w-30 Full Synthetic high mileage oil

Thanks

 

i recently noticed mine making a similar (if not, the same) noise as you described. i thought i was tripping at first but i think it might be that pcv valve that everyone talks about

 

I'm going to plant this here because there is a TSB for the '12-'14 V6 engines. My '14 developed the knock at about 20k mi. or so and I was going to have the TSB done but others have reported that the TSB made it worse, and some said it made it better so IDK. The TSB is at the bottom of this post.

OP I know yours is a 2009 and not subject to the TSB. And lets hope that it is not one of the more serious engine problems that have been showing up here as of late.

In a broader sense the 4.0 engine has a pretty high compression ratio and any carbon build up on the top of the pistons can create hot spots causing early ignition. One has to also wonder about the goofy fuel blends showing up seasonally all over the place.

A couple of things to try would be to clean the upper combustion chamber with something ranging from steam (and/or very small doses of water, don't want to hydrolock) to something more serious such as the older GM top cylinder cleaner in order to get the pistons clean and then use a higher octane top tier gasoline. On mine I just used repeated doses of the Techron concentrate and that helped for a while but I noticed that it is starting to return.

T-SB-0044-14.pdf

 

I had this TSB applied to my 14' and it helped out quite a bit. It didn't eliminate it though as I still hear occasional knocking under acceleration on an incline. What helped the knocking was using higher octane fuel (which I've stopped using since I rarely encounter the knock now).

I read that a few people with 15' Tacoma's were getting the knock, but no software update is available to address. My guess is that the 15's had the TSB applied, but still have some knock like I do. I also recall reading somewhere that the 15' have a slightly different software than the rest.

Anyway, try a higher octane to see if that bandaids it, but if it's something that just came about, it would be better to troubleshoot the cause.

 

I did try a higher octane to no resolution. Also tried seafoam in the gas tank to see if there are any benefits to such.

Thanks for all the input so far. Really appreciate it

I wonder if

$24 BG 44k Fuel System Cleaner Power Enhancer 11oz.

BG 44k would help in this instance adding it to the tank. I will buy a can and update you all shortly to see if this has any effect.

 

The minor rattling/pinging noise is normal, and only happens occasionally at roughly 1500 RPM under light loads (ie. going up a slight incline).

All manufacturers have unaddressed, latent defects (some very significantly worse than what we have with Toyota) which aren't safety related (usually all manufacturers fix safety issues unless its Jeep/Chrylser..they just band-aid exploding gas tanks with a tow-hitch). This is one of Toyota's minor performance defects for the 2005-2011 owners, but its not going to destroy the engine or cause long term issues.

What I've done to mitigate - try some different gas stations, and find one that causes the little to no pinging, and stick with that brand. In my area, use of Speedway (which was Hess), consistently avoids the pinging noise in my engine.

 

Automatic or manual?

 

Automatic

 

Interesting thread... It's happening on my truck aswell and I thought maybe the spark plugs needed replacing... Aren't they good for 60,000 mi / 100,000 km?
I'm past that now, bought mine when it was 3 yes old, not sure it's still running on the same plugs but I'll get those done at the dealership (as well as a few other things) and report back on this thread soon.