Posted by Joe in SLO on September 10, 02 at 13:29:10:
In Reply to: 91Burb 350 TBI- No check engine light posted by Dexter on September 10, 02 at 11:38:28:
You can jump the "A" and "B" terminals on the underdash ALDL connector to put the computer in various diagnostic modes. Connecting A and B together, with the ignition key in the "on" position, and the engine not running will activate the diagnostic mode.
Connecting a 3.9K ohm resistor across the A & B terminals will put the ECM into back up mode. The ECM will only use the TPS, engine speed, and CST to activate the injectors. This mode is automatically activated if there is a major ECM failure.
When a 10K ohm resistor is connected to the A & B terminals the ECM will go into a closed loop. The internal timer will be ignored, the engine speed is fixed at around 1000 rpm and the IAC will be in a fixed position. This mode is helpful when trying to diagnose a unstable idle. With the IAC in a fixed position and the idle still continues to fluctuate its probably not a faulty IAC motor.
Maybe that will help you find your miss???
Joe