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    Thread: 1986 Jetta 8v rough idle after changing alternator

    1. 10-09-2019 08:36 AM #1
      So I’ve searched and searched the forums and maybe I missed something while doing research but every issue I seem to come across on this does not seem to be exactly what is going on with my car and before I go and start replacing a bunch of parts I figured I’d post here. So I have a 1986 Jetta 8v with an aba SERP setup on it my alternator went bad and when I replaced it with the new the car started to idle rough. Another thing that happens is when I first go to start the car after it’s been sitting for awhile the car will start up but immediately die when I try to start the car again immediately after the car will start up but idle rough the idle will start to get better after I drive the car for awhile but then when I shut the car off and start it again the same issue will happen with the rough idle. Could this be my warm up regulator??

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    3. 10-09-2019 05:01 PM #2
      Also the idle will sometimes bounce around from 1250 to 750 when I got the car it used to idle at 1250 so could it be my idle air stabilizer valve?

    4. Member
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      10-09-2019 06:00 PM #3
      If equipped with throttle position switches check to see they are working, the idle switch can cause in speed to increase to about approx. 1200Rpm and then drop down to normal idle speed and repeat and then fix itself only to come back later.

    5. 10-09-2019 06:25 PM #4
      Quote Originally Posted by GTI's View Post
      If equipped with throttle position switches check to see they are working, the idle switch can cause in speed to increase to about approx. 1200Rpm and then drop down to normal idle speed and repeat and then fix itself only to come back later.
      Where would the throttle switches be located I’m new to the 8v motor!

    6. Member
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      10-09-2019 08:35 PM #5
      Quote Originally Posted by willjake999 View Post
      Where would the throttle switches be located Im new to the 8v motor!
      Only on some 8v with the engine codes listed

      http://vnc.thewpp.ca/stuff/bentley/e...1/ch6.1.2.html

      Engine code can be found here


    7. 10-09-2019 10:50 PM #6
      Quote Originally Posted by GTI's View Post
      Quote Originally Posted by willjake999 View Post
      Where would the throttle switches be located I’m new to the 8v motor!
      Only on some 8v with the engine codes listed

      http://vnc.thewpp.ca/stuff/bentley/e...1/ch6.1.2.html

      Engine code can be found here

      Okay I will check tomorrow and let you know if I have any luck thank you !

    8. Junior Member bellsprout's Avatar
      Join Date
      Sep 12th, 2010
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      Asheville, NC
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      Vehicles
      2k2 GTI 1.8t {sold} // 2010 GTI Autobahn {sold} // 1990 Mk2 golf 8v
      10-09-2019 11:31 PM #7
      I feel like i am having the same issue with the RV motor code not listed on previous posts.

      I have the rpm "bounce" effect from 1200 to 700,

      Trying to find if the RV even has idle control switches.

    9. 10-10-2019 12:05 PM #8
      Quote Originally Posted by GTI's View Post
      Quote Originally Posted by willjake999 View Post
      Where would the throttle switches be located I’m new to the 8v motor!
      Only on some 8v with the engine codes listed

      http://vnc.thewpp.ca/stuff/bentley/e...1/ch6.1.2.html

      Engine code can be found here

      So I found two codes one on the head is 3me and the one in the trunk is GX

    10. Member
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      10-10-2019 01:12 PM #9
      GX code is what the car came with based on trunk tag but after 30+ years who know what in it now. The switches are easy to spot the link shows them.. here are more picture from an RD 8V





    11. 10-12-2019 11:39 PM #10
      When using 90amp serp setup.. keep in mind to check your grounds.

      also isv always go bad.


      Sent from my iPhone using Tapatalk
      3rd vortex name in 20yrs. mk1 & mk2

    12. Yesterday 05:13 PM #11
      Quote Originally Posted by A2JettaTurbo View Post
      When using 90amp serp setup.. keep in mind to check your grounds.

      also isv always go bad.


      Sent from my iPhone using Tapatalk
      I was thinking it was most likely my isv I’m going to put a new one in soon when searching for my throttle switches I honestly couldn’t find them they were probably in front of my face but I will keep an update

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