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

I have 120,000 miles, which seems to be typical from this thread.

Also, I've been monitoring for three days under all or my normal driving conditions and this seems to have fixed the problem.

Apparently I spoke too soon. In general, cleaning out the egr tube and manifold helped significantly. Besides what appeared to be an end to the knocking, the ice seems in general to be running much more smoothly.

However, on Monday, after sitting in traffic for 20+ minutes on a hot day with the air conditioner running, the problem returned, and this time the knocking was unmistakable and worse than I had ever heard it before. Since I had the ac on, the battery had drained down to 2 bars, and the ice started up. When pressing the accelerator, even a little (halfway up the _left_ side of the Eco zone), it sounded like someone had just released 10000 marbles into my cylinders.

This condition continued every time I pressed the accelerator until the battery was charged enough that the ice shut off. Once out of traffic, I accelerated normally and all has been fine since that point.

The following day I was in very similar conditions (hot, ac on, creeping in traffic). I drained the battery down and the ice started. But this time all was normal. I have been unable to reproduce the problem since.

Suspecting this was heat related, I hooked up my engine link and monitored the temperature. Even when creeping in traffic the day I was unable to reproduce them problem, the coolant temperature never went above 197 F.

Any thoughts?

 

If you bad egr clogging, maybe there's some still in there? Beyond what you could reach?

 

Definitely a possibility. I'll take another hack at it. It's pretty easy getting everything apart so I don't mind repeating the job.

 

Well, you motivated me: I finally pulled the air filter box and had look under, at that egr pipe. Had minor build-up, but we've only got around 45000 km. I cleaned that pipe, and what I could reach at the two connection points, but I wonder what's up and down stream. OTOH, maybe the pipe's the pinch point, the worst?

 

Well, the knocking came back. I cleaned the tube again. It was clogged up again. I tried to get inside the EGR itself as best I could. I used a muzzle brush with a flexible piece of tubing on the end. Of course, I wasn't to aggressive because I was afraid of having the brush get stuck and come off.

... This seemed to work again. For a while. I assume now the gunk is in the EGR itself and I'm only getting bits and pieces of it. Perhaps I need to remove the valve itself and give it a thorough cleaning.

 

Next time I have a look, I'm thinking to get some pipe cleaners. You know: the flexible wire with bristles, traditionally made for cleaning tobacco pipes? Nowadays they're mostly relegated to art supply stores I think, used by kids for sculpture projects.

 

A good blow with compressed air through a very small vent seemed to do the trick for me.

 

and after how many miles you had this problem again?

 

Around a thousand. Of course, it doesn't happen often, typically in hot weather when I've been creeping along in traffic for a while. Perhaps it's cooling system related?

 

This is weird. Do you have oil consumption? Do you use quality fuel with techron? Did you check spark plugs for deposits?

 

Are you guys who are experiencing this EGR clogging all using synthetic engine oils?

I'm wondering if this might be a common factor...

And I right in believing that the combustion process of synthetic oils is completely different from that of dino / mineral oils? If it wasn't for the plastic IM, I'd say insulate the EGR pipe to keep it hot, but in your models, I wouldn't do that.

 

As far as I know 0W20 comes only as full synthetic, even 5W30 that some are using will probably be synthetic in 99% of the time.

 

Yes, there is some oil consumption. About a quart every four thousand miles, so not much. Spark plugs were recently replaced and the old ones looked very good with no deposits.

 

I'm at about 120K mi in a 2010 I bought with about 85K mi here in Southern California. I've been noticing the knocking a bit here and there along with oil consumption so this fix is looking pretty promising Never would've guessed the air intake, but it's a lot cheaper and DIYable than the things I was thinking.
When the knocking starts up during significant acceleration I can feel a pull-back in power, I'm not sure if the knocking issue would mechanically cause this, or if the car is cutting the throttle slightly (in which case I would think a code would get thrown, but I get no feedback about it.)

I'll this fix a try (hopefully sooner than later) and report back.

DANKJEWEL KORTENBACH!!

Just to be clear for the Yanks reading this thread... "premium" fuel here in the states refers to 91 or 92 octane which should not be used in the Prius... only top-quality "regular" 87.

 

I used pipe cleaners. They were for cleaning actual pipes you smoke not art work. They were expensive but they were heavy duty. Not at all like art work ones you may have use as a kid. They were designed with sharp tough bristles along them. Compressed air or solvent alone would not unclog the holes on my manifold. I needed to run the pipe cleaners through the holes.

 

Very interesting. I am at 99k right now and have noticed rough idle at low rpm, but no knocking or oil consumption. I do drive mine very hard, so maybe that's helping me with the carbon issue. At this time I have zero oil consumption.

I will clean the pipe and the manifold soon and report back.

 

Very intresting topic! I've been trying to get the intake manifold out for inspection (my 2010 is at 75000 miles), however I ran into 1 (probably) little hurdle that I cannot seem to take. On the intake manifold there (from the middle its located a little to the left)is a connection point where a bundle of electrical wires is secured to the manifold through some plastic fastener. I must have overlooked something, but I couldn't find a way to get that bundle of electrical wires disconnected from the intake manifold? What way is there to get this done?

 

Think I know what you mean, regarding the plastic coupling, and it blocking access to pipe flange bolt, at the intake mainifold end? I've got it off, it's doable, but it is royal, back-breaking pain, with very little clearance. Persevere, it can be done.

 

I found a picture and circled what I meant. I think you were thinking about the same. It doesn't have a fastener or bolt I've seen in other parts in this car. I'm just not sure where to start and with what tool. How did you get it off?

 

Sorry, the connection I'm thinking of is in bottom-right corner of that pic. Another pain.