Not quite sure where this should go, but ive battled idle surge issue for a long long time. Finally realized with battery charger hooked to it, it does not surge. Unhook charger and it begins to surge. If I unhook the alternator it will continue to run. But no longer surge. Im assuming the surge comes from alternator cycling. Would the cure be higher output alternator or just factory replacement? Or is it related to trunk mounted battery?
thanks for any input

 

How old is the alternator ? Sounds like there is a regulator issue with it.
battery voltage does make a noticeable difference when the injectors pulse based on battery voltage offsets in the tuning.

 

I bet 15 years old at least. Not alot of miles. But old

 

Probably has a shorted diode in the rectifier or something; putting lots of AC on the whole electrical system.

As far as "trunk-mounted battery", that might depend somewhat on how it's hooked up; how big all the wires are, where the alt output meets the batt circuit, etc. Lots of opportunities for poor design and/or execution in such things.

 

I'll try another alternator. Taking that out of the equation and everything stabilizes