rpm problems....

1997 ISUZU TROOPER
97,000 MILES
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FIREFIGHTER_661
  • MEMBER
  • 6 POSTS
when my vehicle is in any gear (drive, reverse...etc) the rpms are normal, but when i put it in park or neutral the rpms drop to about 200 then rev to about 1500 then back down and up and down and up. after it reves about three times it then levels back out and does fine. any ideas? also does the transmission run off of vacuum because it is also not shifting normally. all this occured at the same time. i have been fighting this for two weeks and am very frustrated. i am normally good at diagnosing problems and fixing them but this one has me stumped.
Sep 26, 2011 at 12:56 AM
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JACOBANDNICKOLAS
  • AUTOMOTIVE REPAIR CONTRIBUTOR
  • 110,190 POSTS
check for vacuum leaks. The trans is shifted with electric, but I think there is a vacuum modulator on it. If that doesn't fix the issue, check the idle air control valve (IAC).
Sep 26, 2011 at 12:59 AM
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