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Discussion Starter #1
2001 ZX3 zetec and MTX-75 manual

My initial troubleshooting pointed to the speed sensor, but that did not fix the problem. The car would stutter and stumble and the speedometer would jump under anything other than barely pressing the throttle.

Here is what is happening and what I have checked.

Car idles fine

Sitting still when I press on the gas is sputters and the speedometer sometimes jumps. If I floor it briefly it stutters and the speedometer jumps every time. There is also a slight clicking under the dash when this happens. (I read somewhere the ecu may be going bad and rapidly resetting?)

The odometer has been recording distance with the speedometer jumping while sitting still.

Checking voltage, maximum was 15.3 which seemed a little high, so I removed the serpentine belt and unplugged the field wire to the alternator to completely remove it from the equation. Same result

I checked the resistance of the coil, and got les than 1ohm from center to each side of the plug, and 11.2kohms on the secondary from 1-4 and 2-3. So it seems the coil is initially ok.

I gently tugged and played with the connector wires


I can't think of anything else that would muck with the speedometer and odometer while sitting still.

Does the crank position sensor have anything to do with it?

My car does not have abs

Any ideas and tests would be helpful?
 

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Coil pack brother! Swap the coil pack any time the symptom is exactly as yours: the needle 'jumps' and loss of power surging at the same time.
Measuring its resistance wont reveal it's fault always. It will fail under load though.
 

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^^^ quite commonly seen, if you look at the coil (including the base when removed) and see any cracking that would confirm the problem right there.

Drive it enough & eventually a pending code for misfire will show up, you wouldn't even know that was stared in the system without a code reading for pending as well as the "set" codes.
 

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Discussion Starter #5
Thanks! Hopefully this will solve the problem, I am driving the family car to work right now and the wife is not thrilled to be stuck at home. It is kind of amazing that a whiff of something off with emissions will throw a CEL, but the car bucking and almost undriveable does not. At least the VSS was only $58.

Sorry that I ended up with parallel threads, wasn't my intension.
 

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I just finished rewiring a coil harness into my '03 ZX5. Check that harness carefully before you put in the coil...might save you some money since coils are unreturnable after installation.

CELs are designed primarily to alert you to emission problems, or at least that was the original intent. Now they're used by mechanics as an excuse to replace parts at your expense until they find out what's really wrong with your car.
 

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Tx for posting the resolution!
 
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