I always thought my car (truck) TBI would idle rich because it really smells, but after reading another thread maybe it is running lean. THe plugs look good, not indicating rich and no black smoke. I guess when a car runs rich it smells like gas, but mine doesn't really smell like gas, it makes your eyes water!! Is there a way to trick the ecm and make the engine run rich either by manipulating a sensor or somewhere in the prom. I have the capability to burn chips and know some of the prom stuff. How can I reprogram the idle to run richer at idle (in the VE table??). Computer is 7747.

 

While in closed loop the AFR is controlled to the feedback from the O2 sensor. If it is in closed loop the value at $2F7 will allow the idle O2 set point to be increased. This will en-rich the idle.

The conversion of O2 mV to the bin value is:

bin = mV * 0.2304

To rasie the O2 set point by 100mV:

100 * .2304 = 23

Put 23 in location $2F7

RBob.

P.S. the DIY PROM board has more information on GM PROM info then this board. And welcome aboard.