My Prius dead again, with techstream this time.

Hope everything turns up well, grom.

 

I am quite, quite certain that when the tech spoke of "building up and releasing incredible pressure" there were some details being omitted.

There is no way, as I understand it, the fuel system as a whole can withstand pressure or vacuum of more than a handful of inches of mercury either way; the tank itself would balloon out or crumple like a soda can.

Hence my suspicion that the "incredible pressure" happened very quickly and locally: the purge line introduced some fuel-vapor-laden air into the manifold at an inopportune time, like a backfire, and that went boom.

Of course I wish the TSB came with a defect information report the way recalls do, so we could see more of the story.

 

Is it possible to jinx the same problem twice?

 

A quick scan of the repair manual this morning, I didn't find anything to corroborate this. Didn’t look that long though.

Is the new valve a different part number, maybe that’s the reason?

 

While the TSB does say to replace the valve and to update the firmware, that might not necessarily mean it's a changed valve that can't be operated with the old firmware.

To be honest, I don't even see anything in the TSB suggesting the old valve was a different part number. It only says to replace the valve, part number 25860-37020.

It's possible the real magic is in the firmware update (don't open the valve when things would go boom), and the valve is only replaced because it already went boom (as the TSB is only expected to be applied to cars where this has happened).

 

The TSB, specifically, states,

"Repair Procedure 1. Inspect for proper installation of the PCV hose and Purge VSV vacuum line at the throttle body. Ensure the vacuum line is secured at the Purge VSV. If all lines are properly seated, this bulletin does NOT apply. "

So, the TSB only applies, if the hoses are detached like in grom's case. If not, other issues will cause the DTC's.

 

It is noted that the part 25860-37020 applies to the Valve Assy, Vacuum Switching refer to both the categories; PREVIOUS as well as NEW,

while the part numbers directly above refer to Computer, Engine Control (ECM/PCM).

Using the logical structure of the table, the Part 25860-37020 is the same part number that was both used in the original install and was not superseded.

I would aver that the issue was one of quality control for initially installed Part Number 25860-37020 or the particular parameters of each individual car. The software update is so the issue would not happen again, given the number of cars out there that never developed the issue that grom had.

 

l'm sticking to my story that, whatever the technician might have said about "building up and releasing pressure", there is pretty much no way it can be taken literally. The pressure required to blow clamped hoses off nipples could not "build up" in any ordinary sense; other components like the fuel tank wouldn't withstand it.

A key part of the picture is almost certainly going to be that we're not talking about some random unspecified gaseous substance under pressure; it is a mixture of air and gasoline vapor, and if provoked, that s--t goes boom. If that happens locally at the manifold, and the PCV valve does its job and prevents it traveling into the crankcase, and the purge valve prevents it traveling back to the fuel tank, that could be "pressure" enough to blow a couple hoses off.

It seems I only thought I hadn't heard of this TSB before.

 

Sounds like a perfect storm issue. It's like a computer crash that happens only when a exact number of operational parameters come together. Otherwise, it may never happen. It, however, happens enough that a TSB was issued.

It also could be that the over pressure from the mini explosion destroys the evap valve. The valve is likely ruptured.

If the rare perfect storm scenario is true, just replacing the valve without the software up date might be all that is needed.

 

Did anyone else notice the fuel trims in the techstream screen shots?

Post 40 photo 1. around a +20% short and +8% long, which IIRC, means the engine is running leaner than expected based on MAF and fuel expectations, and the computer is trying to add more fuel. I suppose that would be exactly what would happen on a huge vacuum leak, like a hose popping off the intake manifold.

 

TS-Bs are only applied if the concern listed occurs, unfortunately, and within the applicable warranty period.

REVVL V+ 5G ?

 

Actually, it is the new part number only. The reason being they know all affected models have the problem part. For example, in the case of the IM some cars came with the updated one, so they only replace the ones that have the old #s.

REVVL V+ 5G ?

 

I know the $700 is a chunk of money but they are liable to want a majority of it anyway for the tow and firmware update. I would be tempted to keep this repair entirely within their responsibility in the event something else happens.