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Sudden acceleration in reverse

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Old Aug 23rd, 2006, 15:43   #1
bartthib
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Default Sudden acceleration in reverse

A recent terrifying experience: I was parked at local convenience store/gas station. I started my car (1992 940, auto trasmission) and with my foot on the brake shifted into reverse. Immediately the car shot backwards at high speed. I stomped on the brake pedal but it wouldn't budge. I yanked on the wheel to avoid hitting the gas pumps, then jerked the shifter out of reverse through neutral and unintentionally into drive, at which point everything seemed to return to normal. I drove to my local garage where the mechanics checked linkage, motor mounts, and finally decded that dirty transmission fluid must have been the problem.

I've since talked with Volvo service people with long experience who were clueless. Has anybody out there had this experience or heard of it? Any ideas?
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Old Aug 23rd, 2006, 17:10   #2
mollusk
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Hi there, Sounds like you had a bit of a scare!

Sorry to disagree with your garage but I cannot see how dirty transmission oil could cause this. Being totally objective about this it would seem that the problems lies more with the throttle than the gearbox - you say you selected reverse and the car then 'shot backwards' - this can only happen if the throttle is open (or opened). In engaging reverse and passing engine power to the rear wheels it seems like the autobox did exactly what you wanted.

Dirty oil can most certainly cause many problems including sticking selector valves etc. - But it cannot accelerate the car or operate the throttle.

If the throttle was 'stuck' open you would have found this as soon as you started the engine (but it would certainly be worth checking the cable, linkage, pedal etc.).

I am sorry to offer this suggestion but one possibility is something that I have inavertantly done myself - as you depress the brake pedal the outer edge of your foot just catches the throttle and depresses it - as the car moves unexpectedly, you press harder and the throttle opens more - power overcomes the brake - and 'bingo'. The brake and throttle pedal don't share a common pivot shaft so I think it unlikely that they were somehow 'jammed' together but again check for anything in the footwell that may have opened the throttle when applying the brake.

If you cannot find any problems with the throttle system I suspect you may have an 'automatic problem' rather than a '940 problem'. I've not come across this on a 940 before but I have heard of similar cases with 340's and with automatics from many other manufacturers though.

Sorry again to suggest that it might be 'big foot syndrome' but I honestly cannot see how the car could have accelerated away unless the throttle was opened (by a defect, or by a mistake).

Feel free to disagree anyone, any more suggestions ??
If you can add any more clues bartthib do shout.

Mollusk.
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Old Aug 24th, 2006, 01:58   #3
adamsky01
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may i ofer a solution that i found usful as i have done same thing my self





leg left ................................. right leg
BRAKE .................................THROTLE


REMBER THIS AND IT WILL NEVER HAPEN AGAIN

LMAO

Last edited by adamsky01; Aug 24th, 2006 at 02:01.
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