I have an 81 El Camino with a 3.8 Buick V6. It has a computer controlled carb and ESC Distributor. When it is in open loop ie the engine is cold, it runs fine. As soon as the engine warms and it goes into closed loop, it runs rough and when you put a timing light on it, the timing mark jumps all over the place. If I disconnect the mixture control solenoid on the carb, it smooths out and if I disconnect the ESC on the distributor it smooths out.

Any ideas as to the cause would be greatly appreciated.

Thanks

What does the timing do when you have the ESC disconnected? Jump around, or stay steady?

I also ment to ask where is the timing at with the ESC disconnected? The accelerator pump lever also pushes the TPS which is mounted inside of the carb. Make sure it has an operational 190 degree thermostat. In closed loop it will be looking at the o'2 sensor, TPS, MAP,and Coolant temp to adjust the timing and mixture control dwell. The mixture control solenoid should have a dwell of 30 degrees at hot idle. If someone has made a adjustment to the throttle stop screw the TPS could be out of adjustment. Verify the coolant temp sender for the computer is working and in the correct ohm range. Pull the o'2 sensor and clean it with a propane torch as long as it takes to burn off any soot that is on it. Let us know what you find after checking these things.

You got me really thinking back with this one.

Hi Car savy,

Sorry it took so long to get back to you. The base timing is set at 15 deg. I started checking all the controls and found that the map sensor has been removed from the vehicle. I have decided to install a vacuum advance dist. and 4 barrel intake. This will get me by until I get the TPI and 700r4 installed in it.

Thanks for all your knowledge.

Nomaddaddy