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cruise control question


cOoTeR

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So I picked up the new ( to me ) 97 silverado today. I was driving down the highway had the cruise control at 80 started coming up on some slower traffic and tapped the brakes then the cruise didn't kick off. The truck started to accelerate like the throttle was stuck. I'd hit the brakes and the truck would slow down but it would accelerate as soon as I let off the brakes. I tried switching it off (the cruise control) and nothing it kept accelerating. I slid it into neutral and the rpms jumped so I put it back in drive. The only other thing I could think to do other than put it back in neutral and let the engine blow was to stomp on the accelerator and hope it breaks free. It worked. A lil while later I decided to see if it was a freak occurrence and set it again, same result. Any idea what the heck is happening or how I can fix it?

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Ok well first check your your brake switch. Then check your actual cruise control unit under the hood. Make sure the secondary cable isn't a rusty mess. Finally assuming it is factory and not after market I myself would replace the multi function switch. Which is what you use to set the cruise and so forth. Also double check all of your fuses.

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The not being able to turn it off at the cruise control switch over rides the other possibilities. That switch should work, regardless of anything else. Except for an actual mechanical failure right at the throttle linkage. Since pushing the throttle broke it free, I'd look there first.

I had one do that, but it wasn't the same. It easily switched off either way. At the brake pedal or the cruise control. It reset when it turned back on. Two other vehicles with no cruise control did it, and both were stuck throttle linkage.

Edited by ReconRat
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I'm thinking stuck cable between the cruise control servo and throttle body, rather than an electrical cause. Stomping on the gas shouldn't disengage the cruise. Sounds like the cruise shut off with the switch, but the throttle was still hung in whatever position it was in until you stomped it, which broke it free.

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Yeah I hit the breaks pretty hard, I was heading towards slower traffic and thought I was going to hit them. I'll double check that the brake lights work.

The first thing I looked at when I got home were the cables and they looked normal. If I pulled them buy hand with the engine running they would reset like they should but obviously I can't really pull it like the cruise would without reving the engine too high.

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scary.

If the cruise cable is vacuum driven it could be the vacuum switch. When you dropped the hammer on the gas tension would have released on the cruise cable allowing it to un "pop" maybe.

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scary.

If the cruise cable is vacuum driven it could be the vacuum switch. When you dropped the hammer on the gas tension would have released on the cruise cable allowing it to un "pop" maybe.

Yeah, vacuum throttle control. I had one go max throttle till I shut it off.

I think it was a change in pressure outside that did it. Never was sure.

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No idea on a fix, but if this happens again...turn off the motor. You will loose power steering and power brakes but you should be able to get it to the side of the road no problem.

Yes I thought of this afterwards, you know how you get in those oh shit moments and forget the simplest things.

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No idea on a fix, but if this happens again...turn off the motor. You will loose power steering and power brakes but you should be able to get it to the side of the road no problem.

This. Saves you from a blown engine.

Have to know: is it factory cruise, or aftermarket. If it's aftermarket, throw it in the trash.

The factory is all electronic, no vacuum to deal with. The brake switch would be my first though, as I have seen them come apart, and short across, and the cruise unit would think the brakes are off all the time. It's a normally closed switch to the cruise unit, I believe (safest way to do it) and the contacts for the cruise are separate from the brake lights, but in the same (multi pole) switch.The factory unit should be on the firewall, square shaped. If there's a question about whether it is factory, post a pic of it, follow the cable back from the throttle body to find it.

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This. Saves you from a blown engine.

Have to know: is it factory cruise, or aftermarket. If it's aftermarket, throw it in the trash.

The factory is all electronic, no vacuum to deal with. The brake switch would be my first though, as I have seen them come apart, and short across, and the cruise unit would think the brakes are off all the time. It's a normally closed switch to the cruise unit, I believe (safest way to do it) and the contacts for the cruise are separate from the brake lights, but in the same (multi pole) switch.The factory unit should be on the firewall, square shaped. If there's a question about whether it is factory, post a pic of it, follow the cable back from the throttle body to find it.

Ok, as far as I can tell its factory well at least the switch is. I try to look tonight after work.

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