My 1988 350 TPI Trans Am, runs smoother, and doesn't stall when the EST connector is disconnected. With it connected, It idles rough, and stalls every time it is put in reverse, or drive (Auto trans) With it disconnected, it idles smoother, and I can drive the car. What does this mean?

Also, what should the stock timing be set at? What should I see with the timing light? Right now it's at 6 before, on the tab.

 

Anyone???
Could it be the ECM or PROM???

 

I would check the timing with and without the BYPASS (EST) connector closed. Hook up the timing light and open the BYPASS. Start the engine (best to do it with a warm engine).

Check the timing. For an L98 it should be 6* BTDC. And steady. If you rev up the engine the timing will suddenly advance at some point.

Now shut off the engine, and re-connect the BYPASS connector.

Start engine and check the timing. It should be around 22* BTDC after a minute or so. It may jump around +- 6 degrees to help stabilize the idle. That is normal. But be sure that the timing advances over the base setting.

RBob.