1990 buick century

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i have a 1990 century w/3.3l automatic no overdrive, 169,000 miles. i am having a problem with keeping it idling. there are no problems when driving down the road. when we pull up to a stop sign slight pressure is needed on the gas to keep rpms up or it will stall. i have hooked up a scantool while it is running and of course don't know how to interpret all of the data. only codes present are 26 and 27. running in park scantool shows quad drivers 1, 2, 3 bad and 4 ok. while driving 1 and 2 switch to ok. 3 always says bad. what circuits are controlled by the quad drivers and what should i look at next? also did fuel pressure check and it is in range.

posted by  swheeler

A quad driver is an integrated circuit within the ECM which controld voltage output to various devices

http://www.autozone.com/servlet/UiBroker?ForwardPage=az/cds/en_us/0900823d/ 80/0f/18/19/0900823d800f1819.jsp is the troubleshooting chart and a better explanation for the error codes. The actual problem can be anything fron bad wiring connections to a bad ECM

posted by  tbaxleyjr

thanks for the help. still not sure what quad driver three controls. doing some more testing and got some wierd readings from tps. changed that and have only stalled once since. still a problem somewhere but am moving in the right direction.
steve

posted by  swheeler

my car does the same thing can anybody tell me how to fix it :doh:

posted by  plus3store

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