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Topic: Car accelerates on its own... (Read 2772 times) previous topic - next topic

Car accelerates on its own...

Okay i bought this car and have been getting used to all the odd features Mercury puts into them, like the bright light auto dimmer, and the keypad entry, but the cruise control too?? Now when I set cruise control, the car will accelerate to what i click the accelerate to.  I let off gas and it stays steady and hits a hill and starts to speed up.  I step on the brakes a little and it slows down about 25mph and about 2-3sec after releasing brake, the car will assume previous set speed.  Kinda tricky but cool... anyways say i slow down 30-40mph from the speed and car won't speed up, but as soon as i touch the gas pedal, it immediatly resumes acceleration to previous set rate.  Then if that doesn't boggle you, when it is cruising at set speed and i touch gas pedal, it accelerates 5mph increments.  Is this normal??  Kinda reminds me of Herbie, hehe...:screwy:
 

Car accelerates on its own...

Reply #1 –
Doesn't sound normal to me. The cruise control should cancel itself when you tap the brakes and not resume until you press the resume button on the steering wheel. The other symptoms could be normal (the cruise control setup in these cars isn't particularly accurate or sophisticated) but there's definitely a problem if the brakes don't turn it off.

First thing I'd do is check to make sure you still have brake lights. The wire at the brake light switch is known to become brittle and break over time leaving you with no brake lights (and no cruise cancel). Oh, and it's a REAL bitch to get at to fix :hick:
2015 Mustang GT Premium - 5.0, 6-speed, Guard Green - too much awesome for one car

1988 5.0 Thunderbird :birdsmily: SOLD SEPT 11 2010: TC front clip/hood ♣ Body & paint completed Oct 2007 ♣ 3.55 TC rear end and front brakes ♣ TC interior ♣ CHE rear control arms (adjustable lowers) ♣ 2001 Bullitt springs ♣ Energy suspension poly busings ♣ Kenne Brown subframe connectors ♣ CWE engine mounts ♣ Thundercat sequential turn signals ♣ Explorer overhead console (temp/compass display) ♣ 2.25" off-road dual exhaust ♣ T-5 transmission swap completed Jan 2009 ♣

Car accelerates on its own...

Reply #2 –
the cruise control cancel is triggered by the brake light themselves coming on?  i thought it was done off the same switch that told the lights to come on.
91 ranger 2.3 turbo - nowhere near stock
87 thunderbird turbocoupe
06 pontiac g6 gt
:birdsmily:

Car accelerates on its own...

Reply #3 –
Well all my lights work normal.

Car accelerates on its own...

Reply #4 –
Quote from: turboranger91;177615
the cruise control cancel is triggered by the brake light themselves coming on?  i thought it was done off the same switch that told the lights to come on.

It is triggered by the same switch - same wire, in fact (I believe it's green or green with a red stripe). Ergo, if the wire to the switch breaks, you have no brake lights and you have no cruise cancel signal. The wire broke in my car and I did not realize I didn't have brake lights until I stepped on the brake and the cruise didn't cancel - having the car fight you when trying to slow down can be very unnerving...

Ztrane: If your lights are working (note: Just because the signal lights are working does NOT mean the brake lights are working - you need somebody to step on the brake while looking at the lights to make sure they're working) the problem might be in the wire at some point between the switch and the cruise unit, or it might be in the cruise unit itself. Regardless, I'd recommend finding and fixing it ASAP and not using the cruise until you do. Having the cruise not cancel when the brake is applied is dangerous.
2015 Mustang GT Premium - 5.0, 6-speed, Guard Green - too much awesome for one car

1988 5.0 Thunderbird :birdsmily: SOLD SEPT 11 2010: TC front clip/hood ♣ Body & paint completed Oct 2007 ♣ 3.55 TC rear end and front brakes ♣ TC interior ♣ CHE rear control arms (adjustable lowers) ♣ 2001 Bullitt springs ♣ Energy suspension poly busings ♣ Kenne Brown subframe connectors ♣ CWE engine mounts ♣ Thundercat sequential turn signals ♣ Explorer overhead console (temp/compass display) ♣ 2.25" off-road dual exhaust ♣ T-5 transmission swap completed Jan 2009 ♣

Car accelerates on its own...

Reply #5 –
i got you.  i thought you were saying that the cruise control was switched off by being piggy backed onto the wire in the ass of the car. lol. 

the cruise in my car doesn't work at all and neither do my tail lights or dash lights.... these wouldn't be related to each other... would they?
91 ranger 2.3 turbo - nowhere near stock
87 thunderbird turbocoupe
06 pontiac g6 gt
:birdsmily:

Car accelerates on its own...

Reply #6 –
Quote from: Thunder Chicken;177612


First thing I'd do is check to make sure you still have brake lights. The wire at the brake light switch is known to become brittle and break over time leaving you with no brake lights (and no cruise cancel). Oh, and it's a REAL bitch to get at to fix :hick:



I had that happen, twice:hick: . The first time I was able to cut and strip the wire and put a new connector on. The second time it broke it wouldn't reach. I ended up stripping both wires and then soldering a piece of wire to the original wires so they would reach the switch.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

Car accelerates on its own...

Reply #7 –
dont forget the vac switch (half moon shaped) up at the brake pedal.

My cruise is inop as well on this new coug i just got.  Ill have to dig into it as well.

turboranger91
i thought you fixed your cruise? guess not.