toyota prius gen 3 engine knocking solved

welcome anas and thank you. is this the cold start knock that lasts for a few seconds?

or is it knocking under load when driving? thank you.

 

The different spray angles show different levels of constriction in the injector. Any constriction is going to reduce the amount of fuel coming out of the injector and will give a different burn curve. I dont know what knock you are addressing with this demonstration. But as long as the correct amount of fuel enters the combustion chamber with the correct timing of the piston stroke and ignition fire, the engine should not knock no matter what angle the spray is introduced.

So if you are saying that the different spray patterns or level of constriction is causing the knocking, then it is because of the variation in fuel spray volume(fuel to air ratio)and the resulting delayed timing of optimum combustion. However the engines various control units should automatically adjust to this situation.

Just a guess.

YMMV

 

this is a huge discovery anas, many. many people suffer from this problem, and even toyota hasn't been able to solve it. i just hope we have availability of injector service here. thanks again!

 

sorry Anas, but you need to read some more how engines work. the fuel is not directly injected inside cylinders in this engine and the "bad" spray pattern will not cause "multiple sparks".

the cold start knock is simply a misfiring cylinder. i easily replicated that by disabling one spark plug.

 

are you saying one cylinder isn't firing during the cold start knock?

 

yes. probably due to condensed moisture/fuel due to previous short cold run. it can happen in a regular car too, its just it's more noticeable in this hybrid due to feedbacks between ICE and G/Ms.

right, yours could have had a problem with injectors causing misfiring while cold.

the only reason i got a code, the coil was disconnected and ECU saw a problem with lack of current in that circuit.

 

Have others solved the engine knocking problem with cleaning the fuel injectors as this video suggests?

 

I doubt it. Anas premise that the fuel injectors squirt fuel directly into the combustion chamber and onto the piston is not correct. Fuel is injected into the intake manifold for each of the four combustion chambers coinciding with the intake valve opening.

Gasoline engines do not use direct injection, as far as I know, but there may be some. The Prius is certainly not one of them.

 

Hey all,

Bumping this thread to confirm that this works.
I had the same problem.

I started getting this knocking noise mostly when the engine is cold. Noise started getting louder and my fuel economy was dropping. Went from averaging 23 km/l all the way down to 18 km/l. Instant KM/L on the highway was around 20. 23 at best.
Started losing power, especially when going up hills.
Thanks to this thread, I realised that this was the simple fix needed.

When done, instant KM/L on the highway instantly shot up to 30km/l. Noise gone. Car even idles smoother.

Hope this helps anyone having similar issues.

 

I only use Tier One gas which may prevent the problem. My dealer recommends Tier One gas.
Study: Top Tier Gasoline Worth the Extra Price - Consumer Reports

 

Seems like prudent use of Techron would also maintain the injectors enough to prevent something like this.

Also, I think you will get some blowback on your assertion that this 'solves' engine knock. We are a skeptical bunch here.

At any rate, thanks for your contribution!

 

Anything that causes misfiring can make a knocking racket from the engine, and the fuel-injection system is one of the three usual suspects for misfiring. Bad injector spray patterns can be a cause—not because of "making multiple sparks", as has been correctly pointed out (because on a Prius they inject into the manifold, not into the combustion chamber), but just because either the injected volume is changed beyond the roughly ±20% the ECM is able to learn, or, worse, the volume change is worse for some injectors than others (because the ECM can only learn an overall fuel trim, not one for each injector). If the pattern changes from a fine spray to more of a squirt, less of the fuel gets atomized into the mixture and the effect is a lot like burning too lean (except that there's also a bunch of unburned fuel in the exhaust, chowing down on the catalytic converter).

So, any given car with a misfiring/knocking problem could have an injector issue, but also could have any of the other issues that cause those symptoms. An easy way to nail down whether it is the injectors or not is to send them to a service that cleans and restores them and provides written before/after test results. On PriusChat, that has been going on for Gen 1 and Gen 2 injectors (they use the same part) for several years now.
You can see examples where the injectors were proven not to be a problem (here, for example), and where the injectors were caught red-handed and shown to be the problem (here, for example).

So far they've been turning out innocent about twice as often as guilty, but the guilty cases do happen.

-Chap

 

Mine was definitely burning way too lean.
On cold start you could have smelt it.

I'm not saying this is the only fix for the issue, but I've had no problems since.
Went from 18km/l to >24km/l for the tank.

 

Just thought I'd share that this seems to have worked for me.

I had occasional pretty bad knocking (like "is my engine actually damaging itself" level bad, soundwise) at start up. Replaced the spark plugs thinking that would be it but it persisted. Decided that $8 on a bottle of Techron would be worth a shot and it hasn't been a problem since. Pretty sure my fuel efficiency has gone up too.

 

Sorry to bump an old thread, but can anyone tell me where I can read up more about the knocking under load? Mine is doing that and I’m not having much search luck, pretty much everything is about the cold start knock.

Thanks!