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Idle fluctuation when coasting?


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Here's a bit of weirdness... Conditions: <30 MPH, off throttle, coasting, usually downhill or level grade. RPM sitting at ~750 RPM, every 4 seconds or so RPM will drop below 500 for about a second, then come back to ~750, then repeat after 4 seconds. Doesn't happen at a stop or in park. Any guesses? ISC motor, dirty throttle butterflies, bad MAF (or is it MAP on a '96?) sensor? O2 sensor?


-Mark P.

Salem, MA

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"Refined Sugar" - '96 SLS, 175K

"...the Caddy is dedicated to relentlessly -- and comfortably -- converting time into distance." -J.J. Gertler

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There is no ISC motor on the 96, that was my first thought also until I saw 96. Try taking out the IAC (Idle Air Control) on the side of the throttle body and cleaning it and its passage.

IAC is #1


Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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