I have a 1994 JDM GSR with bolt-ons. My problem/question is this:

I properly set my ignition timing by adjusting my idle to factory specification, then I jumped the service connector, then I connected my timing light and set my timing to 17 degrees BTDC.

After disconnecting the service connector, I rechecked my timing with the idle still set at factory specs. and the timing was now at 15 degrees BTDC. What the heck? By not jumping the service connector, my engine timing was retarded from 17 degrees to 15 degrees. Does this mean that my engine is running at 15 degrees BTDC all the time, except when I check the timing and jump the service connector?

I have heard that by jumping the service connector it helps to give a more accurate timing reading, but this just doesn't make sense why the timing would be retarded so much after I undo the service connector.

Has this happened to anyone else, and would someone care to explain the reasoning behind setting the timing with the service connector jumped.

THank you.

 

knock sensor maybe?

 

The ECU will adjust the timing depending on idle speed, knock sensor readings, other sensors, etc.

 

So this means that I should leave my timing where it is at, or should I set the timing without the service connector jumped?

When you say knock sensor, are you suggesting that the knock sensor is faulty?