Vehicle accelerating on its own and disabling breaks

AUSTINWILLIAMS93

MEMBER
1992 PLYMOUTH ACCLAIM
41,300 MILES

When I start my car it idles high, as if I had the gas floored, but only after driving it for a minute. When I try to stop, it basically disables my breaks to a point that I can only slow down to about 15MpH.
When I was finally able to stop my car and put it into neutral, it revved high and by breaks were red hot, literally. I researched it and found that it could be the throttle cable getting stuck or the throttle body jamming up. Also a vaccum seal could be worn. Im not even sure where to find the throttle. Can I get some assistance in figuring out how to go about fixing this issue?

1 Reply

CARADIODOC

MECHANIC
33,727 POSTS

Problems with the throttle cable and throttle body are extremely rare. You would feel the abnormal movement in the gas pedal. I caused the same real high engine speed on my '88 Grand Caravan when I was diagnosing a cruise control problem. What I did could not happen on its own unless one of the wires going to the servo was rubbed through and grounded.

Start by watching the throttle cable under the hood while a helper works the gas pedal with the engine off. If it releases normally, watch it again when he starts the engine. If it moves on its own, unplug the vacuum hose from the cruise control servo and plug it. If that stops the high engine speed we'll have to diagnose that system.

If the engine speed is still too high look for a vacuum hose that is cracked or disconnected. There's a sticker under the hood that shows the hose routing.