Car Bucks when cruising - MustangForums.com


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Old 04-20-2005, 01:20 PM   #1  
philly3384
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Default Car Bucks when cruising

IM driving normally down the road and the car just starts to buck. Kind of like if u were trying to launch and u let the clutch out to early.. but this is when im cruising in like 2,500 rpms and im confused to what it could be.. then the check engine light comes on and i lose like half the cars power im like o ill just jump out and walk.
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Old 04-20-2005, 01:39 PM   #2  
Grandmaster
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Default RE: Car Bucks when cruising

My Geo Tracker did that before. (I know compleatly different vehicle), but what it was was the cones in my cat broke up and started to clog my exhaust. Replaced my cat and how I no longer have that problem.
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Old 04-20-2005, 01:43 PM   #3  
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Default RE: Car Bucks when cruising

Does it do it at about the same RPM each time? Will it idle ok? Is fuel pressure ok? I would check for loose/damaged wires around the the ignition under the hood. Start with the coil (including the coil to dist), ignition module (those wires usually run straight back to the firewall under the intake on right side. Also, a failing ignition module will cause strange problems, including stalling for no reason, engine cut out - and pick up at cruising speed, no start when hot, etc. It's the grey plastic module on the side of the distributer with a harness coming out of the front. $35-50 for a new one. Hope this helps. One other thing, run your codes and post what comes up . . .
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Old 04-20-2005, 02:30 PM   #4  
philly3384
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Default RE: Car Bucks when cruising

oxygen sensors , vehicle speed sensor is what comes up
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Old 04-20-2005, 03:25 PM   #5  
95_302_StangMan
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Default RE: Car Bucks when cruising

how violetly does it buck, if it is soft then it is probley your distrubutor cap u can get MSD kit for about $20
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Old 04-20-2005, 04:28 PM   #6  
philly3384
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Default RE: Car Bucks when cruising

i just changed it .. it has like 100 miles on it.
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Old 04-21-2005, 04:09 PM   #7  
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Default RE: Car Bucks when cruising

How old are your O2 sensors? That could cause your problem, if memory serves: Bad O2 sensors will leave the ECM in "open Loop", which in your case may result in the engine running rich by default of the computer. This could cause the "bucking". Gas mileage gotten crappy? Rub a finger in your tailpipe, er, . . ., Just check for heavy carbon build up in the exhaust, that would be a sign that it's too rich. I find if you rub your finger inside the pipe, and you can't make out your fingerprint due to the carbon, you might be a little rich. Or, go buy a air/fuel gauge and practice reading the erratic movement to determine the mixture. Does anybody know anything about the "vehicle speed sensor", I've never had to deal with that one.
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Old 04-21-2005, 07:06 PM   #8  
philly3384
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Default RE: Car Bucks when cruising

it connects to the speedo gear in the tranny gives u a read out of speed and i think for the cruise control it sends a volt reading to the iac telling it to raise to keep the rpms up.
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Old 04-21-2005, 07:58 PM   #9  
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Default RE: Car Bucks when cruising

what about the o2 sensors? are they old?
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