Idle and Timing question

You are adjusting the timing while it is under control of the computer. There are special procedures to disable it and set base timing. Get a service manual and follow the correct procedure....

When you checked the timing at idle, did you follow the factory recommended procecure? MOST vehicles that still had adjustable timing and computer controlled ignition (its really a '99? I can't believe anything that late still had distributor-adjustable timing!) require that you either disconnect a sensor, jumper a wire, or do SOMETHING to override the computer and just check the basic mechanical timing. Otherwise, you get into a shoving match with the computer and who knows WHAT you do to the actual timing curve.

Nissans never had any problems with their distributor endowed ECU systems. Just because something new comes along it doesn't necessarily mean it's better, it could just be cheaper to make, hence more profit. I used to have a '50s motorbike 20 yrs ago with magneto ignition and the spark on that was phenomenal compared with the later battery/coil ignition systems of the pre-electronic era. They dropped magnetos because they were very expensive to manufacture, not because of poor performance.

Its not the question of having a distributor- lots of EFI/ECU systems have distributors, but its been > 10 years since *most* of them used the distributor to set or adjust the base timing. That's generally done with a crank position sensor (fixed timing reference) and then the advance curve is adjusted entirely in software. The distributor then does nothing except direct the spark to the correct cylinder, and rotating it in the block does nothing to the timing (but can screw up the phasing of the cap to the rotor, but thats another issue...). The last car I had that used the distributor to control the ECU's view of timing was an 84 Cadillac.

Or the old way of doing it could even be better. Far be it from me to EVER claim that "newer is always better."

Well I do have the factory service manual, but I missed the part where you have to unplug the TPS before checking the timing the first time around.. I guess that's one of the perils of doing this kind of stuff at night in the dark (gotta love winter!). I did it properly tonight and it looks like the timing was set pretty much in the right place anyway, but the idle is still a problem.

I did notice that after disabling the TPS, changing the angle of the distributor still affected the idle speed.. is there any way around this in this car, or is the proper procedure, if one wanted to advance the base timing a little bit, to set timing "to taste" and then set the idle speed to factory spec?