Cliff Cox Posted November 20, 2010 Report Share Posted November 20, 2010 I have a 93 Seville sts 4.6 northstar. It has a misfire/ rough idle.... I have owned it for about a yr. 145xxx miles. Daily driver up in till 3 months ago, then it has been sitting. Also have a Chevy van sat longer with no problems, it runs perfect even after sitting. Same gas (93 octane) in both vehicles. This all started after it sat for a few months, now I wanna start driving it again. I have changed the plugs, wires, air filter, & found no vacuum leaks... The rough running goes away at about 2200 rpms. It runs fine until it is idling or cruising at or under 2200 rpms I was thinking next to clean TB & MAS... Any other ideas/ suggestions????? Link to comment Share on other sites More sharing options...
BodybyFisher Posted November 20, 2010 Report Share Posted November 20, 2010 Check for codes set on your on board diagnostic system Since it sat, check for corrosion in the towers of the coils I would do a compression test Are you losing coolant? 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 Link to comment Share on other sites More sharing options...
Cliff Cox Posted November 21, 2010 Author Report Share Posted November 21, 2010 I will check the post, I looked when I changed the wires & didn't see anything obvious.... It is not losing coolant, the oil isn't milky or discolored at all. I will also check for codes at the same time.... I'll let you know what I find... Thanks !!!1 Link to comment Share on other sites More sharing options...
dmk9561 Posted November 22, 2010 Report Share Posted November 22, 2010 Check your coil packs, especially if power seems down. It leaves no code behind, but is a big smoothness and power problem, Link to comment Share on other sites More sharing options...
BodybyFisher Posted November 22, 2010 Report Share Posted November 22, 2010 Check your coil packs, especially if power seems down. It leaves no code behind, but is a big smoothness and power problem, Good suggestion Here is a link to our coil testing thread http://caddyinfo.ipbhost.com/index.php?showtopic=16967 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 Link to comment Share on other sites More sharing options...
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