1990 GEO PRIZM
120,000 MILES
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CARPETMAN1759
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Have a 90 geo prizm LSI sedan with the 1.6 L .Did alot of repair to engine,now I need to reset the idle correctly. Where can I pull the RPM signal from? Is there a plug that comes off the distributor? I really have not looked yet.
Oct 23, 2012 at 2:47 AM
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RASMATAZ
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Do you have a distributor driven ignition system if so hook up the TACH on the neg. side of the coil and ground
Oct 23, 2012 at 2:53 AM
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CARPETMAN1759
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I know you pull it off the negitive side of the coil but the coil on this motor is internal inside the cap. ??????? There has to be a port somewhere under hood to get it from.This car does not come with a tach option in any model until 92.I would like to put a tachometer on it if I can find a connection.
Oct 23, 2012 at 1:58 PM
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RASMATAZ
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kk-Try this

Warm engine to normal operating temperature. Turn engine off. Remove cover from Data Link Connector (DLC) located on left strut tower. Connect a tachometer to battery and terminal No. 19/IG (Black wire) of DLC. Good Luck

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Oct 23, 2012 at 11:12 PM
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CARPETMAN1759
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OK! I found the data link box,but it is not look like your picture.It only has 17 pins in it.It also has a rubber pull off cover on a pin mounted outside of this box that is marked 1G - . I don't know if that is what you are talking about.Also my prizm is a 1990 1/2 model vin 6 if that matters.I want to make sure before I start sticking meters into wrong connections and short something out. Been there done that! Thanks,
Oct 25, 2012 at 4:12 PM
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RASMATAZ
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Slap the Tach meter on that and read off-
Oct 27, 2012 at 1:19 AM