i had a scanner run on my new engine as some things just dont seem to be quite right, i'm not getting a check engine light but the motor surges. It turns out that the surge is caused by the Generator Field fluctuating between normal and full. I can't seem to find any information on the web (go figure) about what causes this fluctuation. Bad voltage regulator? bad circuit, as its controlled by the ECU? Bad alternator? It's a '98 TJ, 2.5, w/MT and air.
the scanner was a snap on scanner, it triggered every sensor, preheated o2 sensors, tripped all the relays, pulled vacuum on the EGR, checked the cruise control functions (rotated throttle butterfly), fired every injector individually, ran fuel pump, trigger ac clutch to make sure it was working properly.
The only code that the engine had stored was "No Crank Position Sensor Voltage at PCM"
it had a spot where you could turn the "Generator Field" to the off position, normal, or fully load it...the motor started surging when it it went to full, and if you set it to normal it would continuously cycle between full / normal and the motor RPM would jump up and down. When he turned the "Generator Field" OFF, my elec fan would still come on but the motor wouldnt surge. Something is telling the motor it needs more AMP draw which triggers a relay that causes the motor RPM to come up. What i dont know is what would cause this, I also cannot find a voltage regulator for my Jeep. I'm pretty sure its external on the alternator, on mine atleast. '97 - ' 98 were external (i think) then in '99 they went to a one wire alternator
