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Unexpected Accelleration

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Hi Scotty

got a 2006 dodge charger 3.5l V-6 that had it's gas pedal replaced,

and still randomly accellerates when you start to take off from a stand still. It has around 92,900 miles But this dosn't happen all the time. once after the the pedal was replaced and before that I was backing up and it took off into a pole. Luckly the pole is still standing. Please help!

Thanks

 Richard

3 Answers
3

There's been reports of unintended acceleration over the years in several makes and models of cars.

None have been directly linked to the ETC (Electronic Throttle Control) system and there's good reason for that. (some have been linked to the cruise control software but that's a different issue and only happened when cruise control was engaged).

The ETC system has many "Failsafes" and redundancies incorporated into it. That "gas pedal" which you just replaced for an example. It has 2 APP (Accelerator Position Sensors) in it.

Same goes for the Throttle Body with it's TPS (Throttle Position Sensors) and it's TAC (Throttle Actuator Control) motor sensor.

All of these sensors send voltage signals to the computer and unlike a misfire code, the computer doesn't wait for 2 events to trip an ETC related DTC (code). (CEL ((Check engine light ON))

When the computer sees a discrepancy in the ETC system's sensors, even for just for a fraction of a second, it throws a DTC and illuminates the the CEL.

Moreover, if the voltage signals differ just a tiny "acceptable" limit, the Computer shuts the throttle body plate and your engine returns to idle rpms and stays there no matter if you push the "gas pedal" or not.

So what would it take for any of the ETC sensors to cause unintended acceleration?

If you only took only 1 thing away from my long-winded diatribe, I hope that it's, "the ETC sensors don't control acceleration (or any throttle plate positions for that matter) the computer does" that.

Individual sensors in the ETC can't do that.

So we're left with the computer.

Now, let's take a look at your complaint: "randomly accelerates when you start to take off from a stand still", AND, "I was backing up and it took off into a pole.

Even though you drive a Dodge Charger, I doubt you put the pedal to the floor and burn rubber each time a traffic light turns green or you're backing up.

More likely, you're accelerating at a reasonable, safe, pace.

So in both of these scenarios the "Unexpected Acceleration" occurred at lower rpms.

One thing that's going on at lower rpms is your alternator charging is lower than at higher rpms.

At lower rpms the vehicle depends on both the alternator (and the alternator circuit) AND a good battery (and battery connections) to provide voltage to the vehicle's electrical circuits, including the computer.
Now, what could cause a computer to go "wonky"?

Well, low input voltage is one reason.

I'm not the type of mechanic who believes in "swapping out parts until you stumble upon the problem", but you're having an issue that can get somebody killed.

You have a 15 year old car with a serious intermittent issue and I'm not comfortable saying, "wait for the issue to repeat itself and then try to run it down".

Somebody could get killed while you're "trying to run this down".

So, you may not find even a handful of people who agree with me. To them I say, "You explain it, I'll listen".

I'd replace the alternator, the battery, and the heavy gauge wires from the battery to the alternator and from the battery to the underhood fuse box.

I'd replace the battery ground wires going from the battery Neg post to the body and to the engine. (cleaning up those connection points).

I understand that I'm proposing to spend around $400...... maybe just consider my advice and take it for what it's worth

 

 

 

 

 

 

 

 

2

This was a problem affecting Toyota electronic accelerator pedals a little while ago.  At first, they thought it was the floor mat interfering with the pedal but it turned out to be the pedal potentiometer itself.  Check for recalls and just to be safe, check your floor mat.  A potentiometer is like a light dimmer switch.

1

The next time it happens, your first reaction should be to shift immediately into neutral & cover the brake pedal. 

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