993 uncontrolled accelleration

EDL0944 · 09-01-2011, 04:50 AM

I have a 96 993 cab that treated me rather rudely a couple of months ago. I was driving at 60mph when i decided to engage the cruise control and immediately the accelerator pedal went to the floor without my foot adding any pressure. I attempted to disengage the system with the control stalk on the column and the only way it would disengage was by holding the stalk in the full off position - if i relaxed the control stalk to neutral then the pedal would go to the floor again. After about five minutes of cycling the systen on and off with the control stalk the system failed and I regained full control. Now it is Kaput and i suppose some expensive system control module is in order. Luckily there was no damage done as the traffic was light and having spent a career in aircraft maintenance test flying etc. I just dealt with it. I am wondering if this has happened to anyone else or if this is the one in a million failure. I sent a description of the incident off to Porsche and have heard nothing back. My email is edl1@hargray.com Eric

toddu · 09-01-2011, 05:09 AM

Isn't that the unfortunate way the cruise control fails on these (older) cars??

Todd

daniel911T · daniel911T's Garage

HIJACK ALERT Squak 7500!

Just to commiserate....
I had a problem with my accelerator lever, a metal part in the pedal cluster connected to the pedal and the accelerator linkage, dying from metal fatigue.

I was driving along the freeway in my '69, and was gently accelerating at about 3/4 throttle, crested a little hill, and the accelerator would not return!

I mistakenly pushed the clutch... the motor was instantly on the MSD rev limiter at 7K (which is a bit fast for a T) I reengaged the clutch, got the revs under control, and kept driving until I was in a place with a shoulder, dragging the brakes to keep speed something near safe.

I finally was able to find a nice wide shoulder, pull over and kill the engine by stopping with the the car in gear. The lever had bent and caught on a piece of the body. I got out a huge screwdriver I had handy, bent the part back, and carefully drove home. (That part got replaced before the car drove again!)

That was my first, and hopefully last, time with a stuck accelerator. It gets the heart pumping. Good thing our little cars have stronger brakes than engines!

Carry on!

Resume 1200

-Dan

88911coupe · 09-01-2011, 05:38 AM

Never had that exact problem but in my '88 one time when I hit the brakes and depreseed the clutch the engine shot up to redline! I realized that the cruise was not disengaging even though the brakes were pressed. I just reached down and used the stalk to turn it off. I suspect is was due to the poorly designed hydraulic brake light/circuit sensors that are used on my car. I've used the cruise only very rarely since and was really just trying to see if it would do it again after I replaced the pressure sensors...it worked fine after that but I still don't use the cruise.

Caferacer · 09-01-2011, 05:47 AM

This exact scenario happened in my '85 Wagoneer Limited (Severely Limited) many years ago. The vacuum system that controlled the cruise control got out of whack and the car would just accelerate out of the blue at highway speeds. It is a pretty unnerving feeling to have the gas pedal move under your foot like there is a ghost in the machine. Rather than pay for an expensive repair or replacement, I had my mechanic disconnect the system and the problem went away. As did my cruise control.