Prius III engine knocking at high torque low RPM (solved)

Hi Kortenbach,

Thanks for sharing the details and the pix . How many km has your car logged in prior to you effecting the clean up?

I seem to have similar knocking issues , which usually occurs when the engine is running hot . It usually occurs while the engine is charging the traction batteries and as I accelerate the car from rest gradually ,the engine begins to knock at low rpm . The knocking does go away at higher rpm .

The other occasion of engine knocking occurs when i release the accelerator rapidly after accelerating the car to a higher speed .Is the knocking pattern similar? Any advise ?

Can your clean up procedure be done by a laymen, like me a handyman but not a car technician. My car has
logged in 80k km.

 

Thank you for posting this! I just bought 2010 model gen 3 Prius (130.000 km) and noticed the same symptoms. This is also European Prius (Originally from Netherlands). No fault codes or any other malfunctions were present (yet), just very little shaking when driving on highway steadily around 80-100 km/h and when the engine is settling down at low rpm and lot of torque is taken out. In every other driving conditions the engine was runnig perfectly.

After I found this article, I immediatly checked out the intake manifold and EGR piping. There was the same situation as is described in the above pictures. No any blocking plates were existing but the whole EGR and intake manifold's pipelines were full of sticky black oil/carbon mix. One cylinder's EGR pipeline was fully glogged and I used old toothbrush and compressed air to blow it free.

This worked for me and now the shaking is totally gone in all engine running conditions! I'm afraid that I'll have to do this again after 100.000 km, because the actual root cause is still existing. This whole issue reminds me about the D4D engines EGR malfunction symptoms. The only officially working solution is to clean the system every now and then.

 

This is all weird. Euro Prius have the problem, while US ones don't. I actually thought modern engines use valve overlapping to simulate the function of EGR valve. If so, why need for EGR piping?

 

I was having the same problem. Gen III with 120,000 miles. I did what you suggested and took off the manifold. I took every thing off the manifold and used pipe cleaners on the 4 little holes. They were completely clogged. Unlike yours mine wasn't badly clogged at the point you show in the picture. After I got them unclogged I used purple power degreaser and let it soak 5min then took the garden hose to it since now it was just the plastic manifold with all the electronics off of it. After sticking the hose in the hole you show in your picture of the clog the water would shot out the little holes. This means if those are clogged then the egr system isn't passing exhaust. Thank you for the write up. I was getting pretty discourage with knocking engine. I wonder if the new manifold they have in the tsb about knocking when starting up would not get so clogged.

 

So I take it the procedure improved things?

 

I performed a similar cleaning on mine. (No EGR blocking device on mine). I posted some photos of the inlet manifold which looked much cleaner than the ones above. A good argument for using premium fuel.

 

I have not had this problem, but it can occur give the wrong set of circumstances, i.e. low quality fuel, short trip operation, cold environment. Before going through the effort of removing the intake manifold, it would be worth doing a "fuel induction cleaning service". I have not used it, but there is a $35.00 DIY kit from 3M Corp. that is described in the below article; or, the service can be performed at a repair shop with various types of systems and prices.


How to Clean an Air/Fuel Intake System: The Family Handyman

 

To the OP: browsing through the repair manual: there's a lot of electronic logic controlling how the EGR valve operates. It's not supposed to run constantly, at full capacity. Could it be there's something wrong electronically? But then wouldn't there be warning lights, codes?

And per other responders: what's your mileage?

 

Modern electronically controlled EGR valves have a feedback position sensor. If the valve does not open to the commanded position a fault code should show up.
If EGR 'air' and 'Crankcase Ventilation' vapors meet and mix within the intake manifold, they can build up on the inner surface as an asphalt-like substance. This is what was seen in the OP pictures.
The EGR valve can be opening and closing fine but clogged up intake manifold passages keep the EGR 'air' from doing its job. ( I have read the Prius is the only Toyota still using EGR. Is this true?)
(A friend's Prius had an EGR valve go bad. After it was replaced the fuel economy improved. No word if the shop cleaned the intake also.)

No amount of spray on product or fuel additive is going to clean these deposits.
They are small channels from the EGR valve.
They are after the combustion process for the EGR, and before the fuel injectors for fuel additives.
Removing and mechanically cleaning the intake manifold may be the only way to fix it.

I guess the questions are:
> How big of an improvement did the intake manifold cleaning do for fuel economy and engine performance?
> Shouldn't the knock sensor keep the engine from getting into that area of performance, but result in degraded performance/fuel economy? ( Have high miles owners seen a FE reduction with miles?)
> Is this build up of deposits a common problem with high miles Prius's?

 

I didn't notice an improvement but I also didn't notice any drop off of FE before cleaning. I did mine as a routine maintenance project.

 

Spiderman the knocking and shaking is gone on mine after the manifold cleaning and it's not burning oil like it was. Could a blocked egr system lead to oil consumption? I'm thinking this all stems from a bad intake manifold design. The tsb on the intake manifold for my vintage of prius talks about water condensation build up because of the design and on a cold morning you get misfires and a very noisy startup. I started experiencing that startup problem at about 80k miles. I should have taken it in then but I'm in pa and it was just out of the covered mileage. They would put a newly designed manifold on 1.5 hours labor $245 for the manifold all covered by the tsb. After the bad startups I started getting the knocking and shaking when I was going about 25mph up hills. I would recommend getting the new manifold if you have the opportunity. If your out west they cover you for a long time 180k or something like that. I say Toyota should just fix all of them. Save us the trouble of cleaning them out periodically. The knocking and shaking just gets worse and worse where you're ready to junk the car. With that knowledge you can probably get a deal on a used one someone can't figure out how to fix. Btw mine didn't have a mod either. It was dry and sooty towards the egr valve and like wet asphalt in the 4 little holes in the intake manifold.

 

I can't say with scientific certainty but I again wonder if using premium is why my car avoided this problem. while I did have sooty blockage, it was dry and easy to scrape and blow out with compressed air. There was some clean oiliness in the head intake which is most likely because of the way the Atkinson cycle works.

 

These are my exact symptoms. I just hit the 120k mark. New plugs didn't help for me either. It looks like I have a project for this weekend!

 

Interesting, so it's not just European cars with this problem. I don't recall this being a problem in previous gen, this must be new issue for gen 3, right?

 

The build up will occur with all EGR systems, but the associated problems may vary with each individual vehicle. Some vehicles may never show symptoms.

 

I cleaned out the EGR tube yesterday. It was nearly totally blocked. So far, results are inconclusive. I thought I heard some knocking earlier today but this was with the a/c blasting, the radio on, and lots of road noise. The knocking I heard before was unmistakably loud. I'll keep monitoring.

 

Did you clean the EGR passages in the manifold as well?

 

I did. So far, I haven't heard the knocking. I'm beginning to think what thought I was hearing yesterday was just environmental noise.

 

Let's hope!!

 

What mileage do you have? I'm curious how long it takes to get to this state, how often it would be worth checking.