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Old 08-14-2015, 05:35 PM   #1
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Weird speedometer problem

Hi I have a 1994 gt and occasionally the speedometer will go crazy and start going up and down.Also a couple times my car randomly shut off when i push the clutch in and slow down, the clock also won't keep the right time idk if their all related? If so what do you think the problem is, a bad ground?


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Old 08-14-2015, 07:57 PM   #2
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I would say you have a bad ground. Check the main grounding strap from the driver's side motor mount to the chassis. For a 21 year old car, if its original, this is very likely at least part of your problem.

Also could be a bad alternator or bad battery. You can have both tested at a local brick and mortar store
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Old 08-17-2015, 06:01 AM   #3
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Also even if the ground looks good from the outside it could be cracked or corroded from the inside.

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Old 08-17-2015, 11:49 AM   #4
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You started another thread which is going to confuse you and others.


Start by learning how to get your codes. It doesn't matter if your check engine light is not on. It is free and a good tool to have as it is a starting point.


http://sbftech.com/index.php/topic,2471.0.html


Check for vacuum leaks which is a major culprit with older cars and wreck havoc on simple things like idle.


When was the last time you did a full tune up. Like plugs, wires, cap, rotor, clean MAF, clean IAC, fuel filter, check and clean grounds, vacuum leak check, check your timing.


These older cars need love as they have been used and put away wet usually.
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Old 08-17-2015, 01:44 PM   #5
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I did all the plugs, wires, cap and rotor about 6 months ago. I clean the throttle body regularly,just got all the fluids changed. I did the fuel filter a year ago and a new air filter about 4 months ago. I'll check for vacuum leaks and clean the maf though next, I had four or five vacuum leaks fixed when I bought the car.


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Old 08-17-2015, 02:35 PM   #6
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Check your codes.
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Old 08-18-2015, 04:21 PM   #7
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Before you extract codes(like smurfstang mentioned)be sure to warm the engine up to operating temp,make sure the ac is turned off and you put the transmission is in neutral.Now run the koeo scan.If you've got code 67 and/or 29,read the info in the appropriate link below to trouble shoot your problem.Having code 67 or 29, in a manual transmission equipped Mustang ,will cause engine stalls.Code 67 deals with the neutral safety switch circuit and code 29 deals with the vehicle speed sensor.The nss and vss are both engine load determiners,so idle strategy is controlled in relation to their inputs.The vss is used to activate the idle dashpot function.The dashpot function is used when you push in the clutch to slow down and come to a stop or when you shift gears.You can read more detailed info about this process in the vss trouble shooting link below.
(NSS Link)
NSS/Clutch Pedal Switch Code 67 Troubleshooting
(VSS Link)
VSS Code 29 Troubleshooting

Make sure you check wire integrity(no nicks,missing insulation, bare or cut wire)and pinout condition (no corrosion, bent pins,broken harness locking tabs)on the CSS(clutch sense switch) NSS(neutral safety switch) & VSS(vehicle speed sensor)wiring harnesses, which can also cause these codes to set as failures.
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