Trouble setting timing 1990 LX 5.0 (EEC keeps readjusting timing when spout put back in to 14-16 degrees BTC)

[taws1961]

I brought the car up to operating temp and shut it off. I took the spout out, loosened the the distributor lock down nut then hooked up the timing light assuring #1 cylinder was selected and arrow pointing toward the spark plug. Turned the car on and adjusted distributor until 10 degree BTC was lined up with mark over harmonic balancer and on the harmonic balancer. I tightened to lock down nut on the distributor assuring that the distributor didn't move while doing so. I rechecking the timing again and it was still at 10 degrees BTC. I the shut the car off and plugged in the spout. I turned the car back on and assumed the EEC had recognized the new setting of the distributor, but it had advanced it to 14-16 degrees BTC. I repeated this process 3 times with the same results. My harmonic balancer is wobbling some, but not enough in my estimation to throw things off too much. Am I missing something else or will EEC continue to advance timing no matter how many times I set it to 10 degrees BTC? 168K Miles......Please help!

 

[7991LXnSHO]

The spout out timing is static or base timing. The spout in allows the computer to adjust timing further as needed on the fly.
Unless your distributor is actually moving and throwing off base timing, it sounds like it is running as it should.

 

[Mustang5L5]

I’ve found that it doesn’t take much to move the timing a few degrees. For example, the act of tightening the bolt down can cause the dist to shift slightly. Also the wiring harness on the TFI can “tug” the distributor back to a spot once you let go of the dist and before tightening it down.

Really need to hold it fast and only loosen the nut up enough to barely be able to rotate it, and then hold and tighten and recheck.

 

[Bullitt347]

I brought the car up to operating temp and shut it off. I took the spout out, loosened the the distributor lock down nut then hooked up the timing light assuring #1 cylinder was selected and arrow pointing toward the spark plug. Turned the car on and adjusted distributor until 10 degree BTC was lined up with mark over harmonic balancer and on the harmonic balancer. I tightened to lock down nut on the distributor assuring that the distributor didn't move while doing so. I rechecking the timing again and it was still at 10 degrees BTC. I the shut the car off and plugged in the spout. I turned the car back on and assumed the EEC had recognized the new setting of the distributor, but it had advanced it to 14-16 degrees BTC. I repeated this process 3 times with the same results. My harmonic balancer is wobbling some, but not enough in my estimation to throw things off too much. Am I missing something else or will EEC continue to advance timing no matter how many times I set it to 10 degrees BTC? 168K Miles......Please help!

You should rev the engine up and down with the spout in and watch the timing. It goes all over the place. This is considered normal...

 

[taws1961]

You should rev the engine up and down with the spout in and watch the timing. It goes all over the place. This is considered normal...

Okay Bullitt thanks......

 

[taws1961]

The spout out timing is static or base timing. The spout in allows the computer to adjust timing further as needed on the fly.
Unless your distributor is actually moving and throwing off base timing, it sounds like it is running as it should.

Okay thank you much

 

[KRUISR]

I’ve found that it doesn’t take much to move the timing a few degrees. For example, the act of tightening the bolt down can cause the dist to shift slightly. Also the wiring harness on the TFI can “tug” the distributor back to a spot once you let go of the dist and before tightening it down.

Really need to hold it fast and only loosen the nut up enough to barely be able to rotate it, and then hold and tighten and recheck.

Mike, OP said he checked again after tightening.

I tightened to lock down nut on the distributor assuring that the distributor didn't move while doing so. I rechecking the timing again and it was still at 10 degrees BTC. I the shut the car off and plugged in the spout.