Rpm? Unstable will not pass smog.

1995 FORD MUSTANG
120,000 MILES • 4.3L • 6 CYL • 2WD
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FRANK WIEST
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  • 1 POST
When you hook the car to the smog machine the rpm levels are very unstable. They jump all over the place. Will not allow machine to test car smog.
Apr 15, 2017 at 6:35 AM
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STRAILER
  • ✓Experienced Mechanic
  • 55,694 POSTS
Hello,

This happens when there is a large vacuum leak somewhere, here is a guide to help you get the problem fixed.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Please let us know what happens.

Best, Ken
Apr 17, 2017 at 9:33 AM
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