I have a problem with 1999 honda accord (with F23A4 swapped motor) , all lights flicker and at same time RPM fluctuates, changed alternators 3 times(used ones), check fuse etc. Lately electrician installed the scanner and turns out alternator is an issue as during test drive voltage drops as low as 12.4V on scanner BUT in stationary position alternator never drops voltage less than 13.4V and putting max load while turning ON head beams, Aircon, entertainment system etc, can anyone explain WHY? Also does this voltage UP n DOAN or flickering of RPM have any impact on ECU driving the fuel system? my understanding is that since voltage is flickering its also disturbing the fuel system as ECU is not able to send stable pulses to fuel system? car runs heavy under 3000RPM but drives like a charm just above 3000RPM? plz help me out of this misery

 

ooops...80 reviews and no suggestions, where are the experts? I am new on forum and was expecting members help?

 

Bad diodes in the Alternator will cause this, Very common thing, I had to change out my alternator 4 times. Does Turning on your Head lights make it stop? I have a similar experience with the last 3 alts to where I am driving and my battery light would flicker on and off at a certain RPM while driving but it would be fine stationary.

 

Did you check out the alt?
I'm going through something very similar right now. '99 Civic with a Y5/Y8 hybrid, 5spd, P28 ecu. This is the 3rd engine I've had in it, but the ecu, harness and alt have stayed with it through both swaps. The alt tested good, but it was just a basic test where they hook to the battery. My dash lights pulse sometimes, and turning the headlights on does not change it. The headlights pulse right along with everything else when its going on. I've had trouble getting it to run like it should and always suspected this could be an issue. Hope I'm not hyjacking, I think maybe we have the same, or very similar issue. I'll keep looking & try to figure it out. When I do I'll let you know.
Gator