NEW!!! Service Bulletin for Engine Knocking at Startup T-SB 0012-10

ugh . . . sorry

 

Well, dealer called. They could not reproduce. But they are going to do both motor mount and intake tsb. Will be a week till I get it back. So kinda a good thing? We'll see once car is back in my garage.


iPhone ?

 

Post the documentation when you get it back.

 

So, is the Gen3 Voltage Boost Converter Recall going to include a software patch to try to fix the transmission knocking at cold start issue?

 

Al.
Just a little clarification on my theory. When I had this problem in late 2012/early 2013 I was getting no help from dealership at all. Same story...leave it here, we have to see it, etc. Before they finally admitted there was a problem in 4/2013, I spend many days trying to recreate the problem in order to tell them how to do it. My humidity cause comes from this example. I have a heated garage that stays around 64° (my long since passed Beagle loved it). On five different occasions, with the outside temp varying from the mid-20's to mid-40's, I could back the car out for one hour to eight hours, with the ICE kicking in each time on the way out and back in. The next morning it never failed to act up. On two occasions I turned the heater off and followed the same pattern. Neither time did the engine run rough. I would have tried more but that's when the dealership finally looked at all the YouTube video that was there in early 2013 and told me to bring it back and leave it. I wrote the instructions on how to make it happen for them. My invoice from that trip states they were able to recreate the problem and the new IM was on order. Weather was much better then so it took until this winter to see it didn't work. Aside from the folks I worked with in the small area of Southern Indiana where we live, as I described previously, the dealership told me they worked with the "engineers" this time and they, too, mentioned humidity and moisture as the problem. I was sceptical that "engineers" had been contacted and a "case" created with them. However, when I called the lady back at ToyotaUSA and told her I had my doubts, she was able to give me the case number. Accordingly, she and I discussed my options at this point and the arbitration option, as described in the Prius manual is next and then, if not satisfied, the Indiana Lemon Law through the state Attorney General. Their office is very interested since I can provide them with three names that I know of for sure and there is another gentleman on here that lives in NW Indiana. I'll contact him to see if he would be willing to take part in the Attorney General actions, if that time comes. I'm not a car expert, just an old retired banker. But, once I got my head wrapped around the humidity issue and started reaing info about it, it finally made sense to me. There may be other issues but I just haven't seen them yet. Have a great day.

 

Hey 1945 steve i assume you are referring to me in NW Indiana. I'm going to try to recreate and document with video my issue over the next few days. My parts came in from the dealer for the TSB but I have not done them yet. So i want to be able to recreate this easily so after the new part is installed i can test and see if it still does it.
I'd be in if you go further with your actions and my car continues the knocking
It def has something to do with not letting the car completely warm up.
When i picked my car up from the dealer after they tried to recreate I assume they started it, moved it outside and it sat in the cold for about 6 hours, when i picked up and started it, there it was the knocking.
i can also think back to my occurrence the day i brought it in to be looked at...We got home from vacation, sister in laws car was in the garage, so the prius was parked outside for about 4 hours. I went out moved it in the garage where it then sat for 2 days (engine kicked on but only took me about 1 minute to get it in the garage). When i started it 2 days later very bad knocking, worst ever actually. Weather was bitterly cold at this time high temps were in the 0 to 10 range over the weekend. My garage is attached but not really heated, stays about 33-40 in there.

I'm going to do this tonight...park outside when i get home, leave it sit until i got to bed, move it in garage seee what happens.

 

That's the way I replicate it. Turn your camera on in the morning and it should capture the problem. I've done it both ways, coming from the warm garage to the outside for a few hours and then back in, and leaving it out for a while after driving somewhere and then moving it into the heated garage. I can only remember once when it didn't make the noise. If this thing goes farther I'll let you know on here. The AG's office is supposed to be sending me some forms to fill out to see if they want to pursue it. Are you tired of shoveling yet? My brother-in-law is living in DeMotte for a little bit and I'm not sure he would want to spend the rest of his working career there. Have a great weekend, we're waiting for the next round of snow this afternoon.

 

There we go, did what I said I was going to do. and caught it on video this morning. I'm going to repeat 2 more times this weekend and get video. Next week I'm having the TSB put on then i'll repeat after the install and see what happens, I assume it'll be same results.

Yes very tired of the snow!! waiting for spring to arrive!

 

Hi there Steve,

Thanks for the great description of how you were able to develop a reliable method for getting your car to start its knocking trick!

I have no doubt about what you say, and think you've done a great job of pinpointing and describing the pattern. I think it now just needs some refinement to work out the cause, now that we know how to easily replicate the problem.

Five out of five is good enough for me! That's actually very interesting and important information. Using your strategy, you've been able to take a rare, sometime event, and create the scenario where it always happens. Great Job! I think you are the first to report this. You da man!

Prior to this, I was thinking there must be a random element to this behaviour, such as, (maybe) it also depends on the crankshaft position, AS WELL as the interrupted ICE warmup, but from what you say, there's now a very high probability that the pattern is entirely consistent and has no random influencing factor, such as engine stopping position. This leads me to suspect the EGR system more than TDC valve overlap - but I could be wrong. I note that in your procedure, you are actually performing two interrupted ICE starts in succession, which is an extremely good strategy. Add to that the garage warmth, and Bingo! Knock-a-knock-knock!

In a way, it's a shame that your dealer intervened at this point. Given the very low frequency at which this problem occurs, two failures to start knocking is not really enough to say that this is a reliable fix, or that it won't start knocking sometimes. Others report knocking under these conditions, when the car has been is "cold soaked" overnight or longer, after an interrupted warm up. I suspect that if you repeat this same procedure but allowed more time (say a day or two), it would probably still happen. I think the garage heater only exacerbates the problem, by actually increasing the "soak temperature" of the exhaust system, such that the water inside it evaporates faster and moves around the system (into the Intake Manifold) more quickly.

In the other cases, I'm sure their exhaust systems are colder during the soak period, so the water doesn't evaporate and migrate into the IM so rapidly, meaning that a longer "soak" period is required to achieve the same effect.

I think the primary factors are one or more interrupted ICE warmups from and at low ambient temperatures, and time "soaking" preferably at warmer temperatures, and maybe ambient humidity, though I suspect this may prove insignificant. (In your cold weather, outside and inside air humidity will be quite low.)

Otherwise, I believe that your findings and reliable method for creating the problem dovetail quite well into my theory.

For one thing, you are now finding that the new design intake manifold doesn't actually solve the problem, even it it's a bit of an improvement. This indicates that the IM itself is not really the cause, and therefore modifying its design and shape is really putting the ambulance at the bottom of the cliff.

It might be interesting to see what happened if you could change the thermal characteristics of the current manifold - though as I don't believe it's really the manifold at fault - I suspect that would be more of a waste of time than anything. Anyway, someone *could* try wrapping the plastic manifold in insulation (to retain heat as per your theory), and see what happens.

However, what you describe only helps to convince me (is this just confirmation bias!!??) that my theory is along the right track.

Clearly, water is getting into the intake manifold, during the time the engine is off. So far, the unanswered questions are: How? And where is it coming from? I say the most rational answers are the most likely to be correct.

After the car has been driving a while, the exhaust system will have fully warmed up, the catalytic converter will be up to temperature, and the mufflers will be hot, along with all the pipes, etc. Any water that was present in the system before will have been evaporated and driven out by the exhaust gas flow. The exhaust system will be hot and dry inside. The only water present will be the relatively small amount of water vapour resulting from the most recent combustion, and this will condense inside the system when as it cools down. Here, the amount of liquid water deposited will be very low, and apparently not enough to cause a problem.

However, when the car has been sitting for a while, everything will have gone cold. Upon starting the ICE, the fuel mixture will be slightly rich, and the amount of water vapour produced will be higher than normal. Because everything is cold, a lot of this water vapour will condense on the cold surfaces inside the exhaust system, causing a build-up of water therein. Because the warmup cycle is interrupted, this water will not be driven out, but will stay sitting in the exhaust system until the next full warmup cycle.

Later, repeating this cold start and interrupted ICE warmup will only tend to add significantly to the accumulation of liquid water inside the exhaust system, providing more raw material to feed, by whatever means, into the IM.

Yes, Steve, I think your research and discoveries are extremely valuable, and I hope they lead Toyota to understanding and fixing this fault for you and all your fellow Prius owners.

Cheers,
KiwiAl

 

P.S.

To understand why this problem doesn't happen all the time, one has to understand how the dew point temperature relates to the humidity inside the IM. Yeah, that's a difficult concept, I struggle with it.

However, I believe there is a simpler way to understand this process.

When the engine is off, the intake manifold is effectively almost completely closed at the outer end by (a) the throttle plate, in the closed position and (b) by the air filter, filter box and downward sloping air intake pipe.

If, as appears to be the case, there is an open path from the exhaust system to the IM, and the IM is closed at the throttle plate, then the exhaust system and the intake manifold could be viewed as "one long pipe", open only at the far end. If this long pipe is water saturated (contains saturated water vapour) along its centre section, over time this water vapour will tend to disperse in both directions along its length. Water vapour will migrate out the tail pipe, and similarly, water vapour will migrate into the IM. If it was closed at both ends, the pipe would eventually become uniformly wet throughout its length. In other words, if there is excess liquid water puddled in the middle of the pipe, some of this puddle will eventually move into the Intake Manifold section.

I think that's what is happening, and the dew point is what makes exhaust gas visible (as steam) on cold days, but not visible on warm ones. Does that help?

 

Our Prii have Atkinson cycle engines where the intake valve remains open during the first part of the compression cycle. So that is a path for exhaust gasses (and the excess moisture) to get into the intake manifold.

JeffD

 

Hi Dr Jeff,

Thanks for your prompt reply.

However, I was under the distinct impression that it is the INTAKE valve that remains open / closes late in the compression phase, in the modern, modified-Atkinson cycle engine. This is mentioned by Patrick Wong somewhere here, and in other places on the web. Patrick mentions this as the reason the throttle valve (plate) tends to get black, due to the recirculating fuel-air mixture flowing around it - though I would have thought that fuel vapour, being an extremely good solvent, would keep it nice and shiny clean... This is how I spotted a car that was misfiring a lot - by the nice clean (bare metal) exhaust pipe.

As I see it, keeping the exhaust valve open late would be very undesirable (though it would obviate any need for an EGR valve) as it would mix a lot of exhaust gases with the new fuel-air charge. Not to mention the risk of ignition due to hot particles in the exhaust gases.

If it's the intake valve that remains open late in the compression phase, I still don't see how that creates a path from the Exhaust system to the IM. The Inlet and Exhaust valves only overlap at around TDC at the end of the exhaust and the start of the intake stroke, and the exhaust valve should be completely closed during the late closing of the intake valve, so I don't see how that path exists.

I would agree that there might be an increased chance (due to the Atkinson cycle changes) of the engine stopping at TDC, hence valve overlap on one cylinder, but I believe that's a low probability event all the same, and would have to be random unless the engine ECU is deliberately stopping the engine at TDC - which would seem a foolish thing for the Toyota engine designers to do?

If I'm right, then doesn't this point to the EGR valve as the likely culprit?

 

Sorry for the typo, it is the intake valve that remains open (corrected in the earlier post). At that time in the cycle, there are still some combustion gas left over from the previous cycle along with the fuel/air mixture pulled in from the intake manifold.

JeffD

 

Yeah, but how does that create a path for water vapour to move into the IM from the exhaust system?

 

I can say that I have tried this.. car sat outside several hours... moved it inside...it sat for 3 days...started it.. and it knocked the worst I have ever had it knock on me. Went on for about 45 seconds before finally stopping

 

Cool...! More confirmation of Steve's procedure and the facts around how to make 'em knock!

That said, I am sure that the knocking noise IS as bad as it sounds. It won't be doing your transmission any good, because it's putting high shock loads on all the gears, bearings and couplings (and the transmission housings) between the ICE and the two MGs. AFAIK, none have actually failed as a result, but I'd bet it's causing greatly increased wear in your transaxle, so I wouldn't allow it to continue, except for evidence gathering.

There is one known and one untested, potential method for stopping the knocking.

1. Put your foot on the accelerator pedal and increase the engine RPM. Whether this moves the system outside its resonant frequency or just pushes the engine to blow the wet spark plug clear much sooner, I don't know. Thanks to Bob Wilson, I think.

2. Yet to be tested, but if it works, seems the better alternative: as soon as ICE / Transaxle starts knocking (with the car safely stopped in your driveway, preferably) put the Transmission into Neutral. See if that works.

If anyone tests #2 and finds that it stops the knocking, Please Let Everyone Know!

 

...I agree.....it's physically impossible to "Bang" two (or more) pieces of metal together, without causing damage (however slight)...... more "Banging", more damage! ......

 

That's why I am worried about this.. What damage has already occurred in the engine or will continue to occur..

 

All,

I have stated before on this thread, that my 2011 Prius has this issue in the winter pretty bad. While it CAN happen more often after short stops, soon after start up, this is not the only way it happens. Heck, my last and worse start up was was directly after a 2 1/2 hour car ride, mainly freeway. We use to own two, 2011 Prius cars and one was way more prone to it than the other car, (still can't explain that one). I currently have a case open with Toyota and waiting word from the regional Rep. on how my local dealership should proceed.

I have had the 050 IM (stock) , the 052 IM and now the 054 IM installed and none of them have fixed or slowed the issue at all. My understudying is that each time the dealer replaced the IM, it was FILLED with water. I was told that this would block air intake needed for combustion and cause one or more cylinders not to fire. Well, at least that is what my dealer has told me. I should hear something later next week and will keep everyone posted.

 

Same here. My second episode happened after a 45 min drive and then sitting for about 25-30 mins.

In my case however, after they replaced my IM, I have not had a re-occurrence.