i HAVE 85 Z28 F 305 700 TRAN I have an idle condition that will not go away till car is brought to stop. Idle, even when car is up to operating temp, holds at aprox 1300 and will cruise all day at this idle if i could. I have driven along back roads and never touched gas pedal. Stop car, shut down and restart and drop in dive and away i go. shifts and drives till I bring car to stop, wait 4 seconds, I can count 1001,1002,1003,1004. and idle drops to about 550-600 and will always return to that rate as long as car is not restarted. I can roll down hill in neutral and idle will not drop till car stops rolling. Had 3 tec1 done and found nothing. However when tech1 is plugged into cig lighter idle goes up to 1200-1300 so i do not think the problem shows. Have had computer,prom,injectors, air flow,o2,iac,tps,coolant temp sensor,speed sensor and plugs ,wires cap and pickup. All to no avail. 2 years ago mechanic found vibration damper had spun on housing so it was changed and timing chain at same time. If anyone has an idea i would appreciate as all the mechanics i have seen are running out of parts to replace. I pasted a while ago but when the vibration damper was found i was assured the timing was set wrong and driving to reset would fix.

 

Have had the same problem for 2 years! Dont have a clue whats causing it. I'm sure someone on the board can help even if nobody had given me an answer yet. If you find out whats causing it feel free to let me know!

/N.

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GTA -89:Free flow muffler,dual 3" HF cats, Edelbrock headers, Vette heads, 1.52 RR 7/16, ZZ-9 cam, Big Mouth, AS&M LTR, !plenum, 52 TB, MSD 6AL, TPIS level V prom, Superior shift-kit and all the minor mods, a AFR 195 headed 383 in the works!! ready May 2001...
http://www.itv.se/tacs/members_cars/m279/m279.html (Swedish Trans Am Club)