1986 VW Jetta Gas

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Old 10-30-13, 02:59 PM
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Cool 1986 VW Jetta Gas

When I cold start the car from overnight sitting the engine surges up and down by 10 thousand rpm. After it warms up it does it a little but not as bad. What do I do to diagnose this? Is there an easy fix? Also the odometer stop clocking miles but I have the speed dial still working? Finding another instrument cluster is next to impossible for this car any suggestions how to get the odometer to read the miles again? Thanks C.
 
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Old 10-30-13, 07:56 PM
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Welcome to the forums.

You mean surges one hundred or maybe one thousand rpm. 10,000 and you would have parts flying around you.

Your vehicle uses an idle control unit and an idle control valve. Usually with age the valve either sticks or gets carboned up or both. You should find it in the air intake manifold.

As far as the odometer.....you'd have to open it up and look for the problem. More then likely you'll find a broken or stripped gear.

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Old 10-31-13, 04:46 AM
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In some of the older vehicles it's possible to replace the odometer portion of the instrument panel. Also on some clusters you can find replacement gears for the ones that strip, but I have a suspicion yours might be a hard find.
 

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Old 10-31-13, 07:49 AM
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Thank you PJMax and The Tow Guy for getting back so quickly, Yes you are right, 500 to 1000 rpm variance, I guess I was over zealous!!! I have been shown this part before but for the life of me cannot find it on the car. You say (in) the intake air manifold? If you could show me a pic of what that looks like and where this valve is I would appreciate it greatly, and where do you buy this? Any auto parts store or is it a dealer item only? Thanks again so much, you cannot imagine the money you have saved me!!! You guys are great!
 
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Old 10-31-13, 07:58 AM
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Also on this Jetta the speedo cable is in a two part series one that goes behind the instrument cluster and ends inside of troff where you remove that plastic cover and screws into a module thing then another cable goes from it to the engine block? Could this be the problem for the odometer not working? And why would the speedometer work and not the odometer? Is there also any alternative to put an exterior odometer on this car for insurance purposes? Maybe a dash mount?
 
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Old 11-02-13, 01:13 PM
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Just wondering the counter box manual transmission that has two cables for the speedometer upper and lower, can this box be illuminated and a single cable go from tranny to speedometer? Where can I find single cable for this car? Please advise. Thanks Chris
 
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Old 11-02-13, 03:47 PM
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Got your PM, but not sure I can be of much help. I'm not really a VW/German car guy. Not familiar with the 2-part speedo cable. Not sure I've ever dealt with anything but a one-piece. If there is only one cable that enters the instrument cluster, then likely the problem is in the cluster and not further downstream other wise speedo AND odo would be inop.

The reason an odo could be inop but speedo still work is that the odo is either driven off the speedo mechanism or has it's own connection to the incoming speedo cable. Broken/stripped gears mentioned earlier or frequently the culprit on these.

At this point I think you best place to investigate is the cluster. I would very carefully open it up and see if anything is immediately obvious. Be careful; at that age there's no telling what pieces/parts could be brittle/worn and easily broken. I know of no "external" odometers.

BTW the idle air unit should be easily found at any good parts house, although they may have to order it.
 
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Old 11-02-13, 05:09 PM
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See if THIS helps you in your quest.
 
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Old 11-03-13, 07:37 AM
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Thanks again guys! Will try alternate VW Forums for my questions. Have a great winter all!!!
 
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