Help Diagnosing Unintended/Uncommanded Acceleration Issue

*cringes*

 

You keep saying you live east of Seattle, and you refuse to leave your car at the dealer to be fixed. Well, I consider you a risk to all the other drivers on the road around where we live, and you're an idiot to keep driving your car knowing you could hurt or kill someone with it if it accelerates by itself.

What is it going to take for you to get it through your head that YOU SHOULD NOT BE DRIVING THIS CAR???

 

Nylion--I will follow this thread to conclusion since the problem is an important one and interests me, but allow me three comments:
a) I've found Galaxie's contributions to this forum to be of the highest caliber--he's trying to help you.
b) This topic seems to have brought out the best and the worst posts I've seen on this forum (the analytical stuff is terrific).
c) As a NON-LAWYER I worry that, by publicly documenting the problem and continuing to drive the vehicle, you have put yourself at risk of legal action should an accident occur. IMHO you need to stop driving the vehicle until the problem is resolved.

Good luck with this and please be kind enough to keep us informed of your progress.

 

Galaxee is a she, and a really cute one too! Her DH is also VERY knowledgeable on the Toyota hybrid system.

 

My apologies to the lady--and thanks for your helpful posts.

 

Correct. Without supporting evidence all you can do is anticipate the possibility and be more careful, or sell the car. Let us know of any developments.

 

G'day mate, sorry to hear about your trouble. this is only an opinion from a mechanic. I would repair the pedal unit myself if the problem was in my own vehicle by inspection and possible replacement of the unit. as you have stated you are mechanically inept my advice would be to simply book the car in over the phone to your local warranty-supported mechanical workshop stating it has a "sticky-throttle issue". it will then become their problem, and will exonerate you from liability in future instances. it could cost you nothing, and certainly has to be worth a try. occam's razor is the mechanics' catch-cry. good luck and best wishes

 

I've gone through the Electrical Diagrams of the NHW20 examining different possibilities. I cannot see where "pressure" on the brake pedal can trigger an acceleration. What I do see is engaging the brake switch on the last little bit of travel can cause an effect.

The only thing that seems to cause the engine to "race" would be a valid acceleration command. Is there anything that would cause the engine to race other than an acceleration command? The degree of acceleration may be a big clue. Very aggressive acceleration would indicate a very different cause than above average acceleration.

I read an interesting B-58 control failure. A gain potentiometer that went to the maximum range actually went slightly off the edge of the wiper. This caused the gain to be zero instead of maximum with sad results. I have no idea if such a condition could occur on a NHW20 accelerator, but something similar might be possible.

ch15 (scroll down to B-58)

 

This is an interesting hypothesis, either a field reversal or a magnetic field 'latch' whereby the magnetic field somehow (pure speculation) finds an alternative path around the Hall effect device sensor. Concurrent with that hypothesis is the a problem with the linear amplifiers that convert the Hall effect voltages into a useful signal. But any hypothesis testing takes 'lab time,' getting a part and seeing how it is made and performs.

Bob Wilson

 

Maybe the OP should stop wearing steel toe boots.

Tom

 

I did an experiment where I kept the throttle depressed but not to the point of activating the "force charge" point and then tried pressing and releasing the break pedal.

With the break pressed the engine went to idle and when released the engine would rev-up and the car would start moving - similar to the OP's description.

It sounds quite plausible that a sticky throttle could could cause the symptoms.

kevin

PS this was on a 2006 Prius

 

It certainly is alienating to see personality comments versus a dispassionate discussion of the symptoms and systems. But right now we have plenty of hypothesis but to go much further, we need a test article or more technical details about the accelerator assembly. Unfortunately, I don't have a dog in that fight.

I have an NHW11, 2003 Prius, and hopefully, will have a ZVH30, 2010 Prius in a month or so. Although I picked up Doug's accelerator refurbishment service, I'm not seeing a good reason for buying an NHW20 accelerator assembly and testing. I don't mind donating my labor but the cost of the part comes from our family account and there is no assurance of ever seeing this cost covered.

I've also speculated about an OBD recorder, which may have utility for my future ZVH30. However, nothing much is going to happen until we get the ZVH30. Again, this would not be 'free' for the OP.

So the ambiguity group remains, in my order of interest:

• accelerator assembly
• hybrid vehicle ECU
• engine ECU
• connectors and wiring
• cruise control interface
• interaction with non-stock, floor mat
• operator error

We have more insights, the brake interaction when the vehicle is stopped. However, we do not have enough data to eliminate all hypothesis.

Bob Wilson

 

Good thinking Bob! we could investigate the possibility of electing a committee to oversee the leasing of a suitable premises to meet and discuss the propagation of a team to look into the plausability of constructing a test-bed laboratory costing millions and taking years or;
we could replace the accelerator pedal.

 

What? Actually performing a sensible experiment? That's actually a very good thing to know. Thanks greatly.

 

nylion, do you drive using one foot, or two?

 

I have a lead on an affordable NHW20 accelerator test article. Knock on wood, we'll have some clues soon enough.

Bob Wilson

 

I'm not sure if I found the right part, but it's the only thing that Champion ToyotaWorld have with 'accelerator pedal' in the description:

Pedal travel sensor, Prius (includes accelerator pedal): MSRP $44.93, discount price $34.15.

Sadly, no illustration.

 

Would it be worth adding the cruise control controls to the suspect list?

ISTR the OP saying that engaging and disengaging the cruise control may have solved the rapid acceleration on one occasion?