Here's a new one:

So I'm driving my '89 IROC in the rain tonight, and I notice some "unexpected acceleration". Not only did the speed of the car increase as though I taking off from a light normally, but I noticed the gas pedal falling beneath my foot. I had to put on the breaks so I didn't hit the car in front of me. It was fine when I was at a light, but when I started coasting again after taking off, I noticed it happening again. Needless to say, this is kinda scary enough to begin with--let alone at night in the rain on a busy city street.

My only guess is faulty cruise control. However, the cruise control has never worked on this car since I've had it (4 years or so). It's never even "kind of" worked; it simply hasn't done anything. The system is still in tact and connected, as far as I know, but it wasn't on when this started happening.

Any ideas?

 

I've always seen cruise control electrically controlling the engine, not physically pulling the throttle cable. I'd be checking the throttle cables for signs of damage.

 

Check your motor mounts.

 

My cruise control pulls the throttle cable - they were designed that way.

Mine works just fine, though sometimes it remembers my cruise - but higher, when I accidently flip the switch to the right (from off), and it takes off.

 

Yeah, I remember when my motor mounts caused me to accelerate, I didn’t even need to put gas, my motor mounts were all I needed to drive around

 

IF you are worried about it, disconnect and plug the vac line to the cruise control servo. The servo is vacuum operated. The amount of vac is controlled via the PWM of two valves.. If something is shorting I suppose it could engage.

 

Or just pop the cruise control cable off the throttle body. It pops right off. Well, mine does but I have a TBI.

Also, yes, cruise control will usually cause the gaspedal to go down. However, my car has a sliding area on the throttle cable connector, so your gas pedal could stay up. But gravity pushes it down.

 

Your car by any chance named "Christine"?

 

Good point! I didn't even think of that

 

Yeah, I'll prob. end up pulling the cable off of the TB.

Are there any tests I can run on the cruise control driving unit (i.e. the thing that actually pulls the throttle) to see where its getting its commands from? This is assuming that it is indeed what is causing the acceleration that coincides with the gas pedal going down without my command. I can't think of anything else that would cause that--the only other thing going to the TB is the TV cable from the tranny. But it pulls in the opposite direction, doesn't it?

I'm actually somewhat pleasantly surprised that the cruise control can do anything at all. I thought it was completely shot. Perhaps it can be revived to come on when I actually WANT it to?

 

There is a 4 (i think) connection plug on the servo. On terminal is common, the rest are to activate the valves. They you can take off the little cover over the valves, and actuate them with a 9 volt battery. If you have the engine running, it should even move the servo.

 

i had the same thing happen to me but in my RS, and i asked about it and everyone told me the cruise control but...mine doesnt have it and never has, so anyone know any other reasons? i just chalked it up to a haunted car lol

 

I had the same thing in my old 82 grand prix 305 4 barrel a few years back , took it to the shop a few times, they never figured it out. I figured it was the cruise control because it always disengaged when I hit the breaks. I searched for a bad wire that was getting wet since it only happened in the rain but never found one so I just disconnected the cruise control. Mine would go almost full throttle when it would happen and never from a stop or under acceleration but only when I was not pushing the gas or the breaks like when slowing down for traffic or a red light. I disconnected the cruise control and never had it happen again.