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So the repair guy experienced this same uncontrolled speed up and he says its ok for you to go out and experiment with it? That's nuts.
You should not be engaging cruise control.
You probably shouldn't even be driving the car.
 

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Having thought about this a bit more, it occured to me that this could be a problem with the cruise control switch. The switch has two wires leading to it. Pushing it in various directions or pushing the button connects 4 different value resistors between the two wires. So it seems like if there's a dirty short between the two wires that intermittently looks like the resistance for increase speed by 1 MPH, and if this short was triggered by vibration from the engine when it's running hard, you could see this sort of behavior.

Maybe your service tech can measure the resistance between the two wires while vibrating the steering wheel?

Anyway, sorry for the misinterpretation. I thought you meant this was the first time they experienced it, especially since you said they agreed it's a problem.

Also, if you are going to continue driving, don't turn on the cruise control. If my speculation pans out, you might not be able to cancel the cruise while it's accidentally shorted to a different resistance. Then you could have uncontrolled acceleration (though I guess the brake pedal should still cancel it in this case).

Good luck getting this cleared up quickly.
 

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Knguyen said:
I wouldn't think this is a reasonable option. Why didn't you slip the transmission into neutral ?.
Hmm, engine at full throttle, transmission in neutral ... sounds like a recipe for a thrown rod to me.

I wonder, can you over rev a diesel?
 

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Hi jsp,
On your trip up Crater Lake, did you pull to the side because you had to (car wouldn't go fast enough), or because you didn't like the accelerator pedal lag (takes a while for car to respond to changes in pedal position)?

On a long uphill stretch you may drain the battery enough that it won't assist anymore. But the engine should still have enough horsepower to maintain "reasonable" speed. However, it takes the engine a while to respond to the accelerator pedal whereas the battery responds immediately if it's got enough charge. So I'm just wondering if you've discovered the limits of "reasonable".
 
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