1988 Geo tracker help

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I have a 1988 Geo tracker. When you start it it revs and then lopes between 1500 and 2000 rpm. It won't idle down. I can move the TPS and make it stable at 2000 rpm. When fluctuating between 1500 and 2000 I pinched off the Map vacuum and it stables out, again at a high rate. If I pop the vacuum off it will idle down and miss. A vacuum guage on the line shows it moving with the rpm. We changed out the o2 sensor(but didn't check the voltage on it). I suspect the map sensor but $250 to try it is expensive. Is there any test for this?? When you drive it, it runs fine above 2000rpm. When loping the butterfly is closed and you can watch it inject fuel to pick itself back up.
Any help would be appreciated.
Thanks

posted by  ronl

Hi Ron,
I have the same problem and I see that you fixed it ,could you please tell me what you found .
thanks Andre

posted by  ajbes

Help please 1989 tracker, idles up and down even when warm

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Also now when driving the car seems like is only running on 3 cyl rather then 4, tried to get a diagnosis on it, but they couldnt find the connectors to do so at the chevy dealership... please help me!!! Stressed!!!

posted by  swtninnocnt88

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