Hondata

I just got a s300v3 in a p28. It's in a civic with b20b swap. So the issue I'm having is that the readings from all the sensors ( map, tps, batt, o2, eld,) is jumping up in down on the smanager gauges and you can see the fluctuation on my hondata app in the sensor list too. I've redone all my grounds. Cleaned and tighted battery terminals and removed all the tape on factory harness to check every inch of wire and the harness seems to be fine. It's almost like wen your using smanager and watching the sensor readings live as the cars running everything fluctuates up and Down and cuts out for a split second then picks back up and it's causing my car to run like crap.the crazy part is I've tested voltage at the wires going into the ecu and at the battery and it doesn't fluctuate on my volt meter. And I've tested the power going to sensors and it doesn't show the fluctuation . It's kinda driving me nuts lol hope someone's had similar prob that I'm missing lol oh and btw I figured maybe it's a bad computer, it is 20 yrs old so I plugged in a stock p72 computer and car runs exactly like it's does with s300 but a little rougher . If u guys could help I would greatly appreciate it. I've kinda new at using s manger so bare with me lol thanks!

Where do you have the grounds connected?
viewtopic.php?f=19&t=5226

I've got a ground coming off the valve cover to the frame. One coming off the ps bracket to frame. Another from trans to frame. And the harness ground by the thermostat housing. All have been cleaned up to make sure has solid connection. I seen that honda has a tsb for the 96-98 civic main power wire from the alt to the fuse box having poor connection so I cleaned those connections up and made sure they were good too. I have a 98 civic 4dr

And just to rule it out the jumper harness I have (obd2 to 1) is brand new and I bought a nice 120$ jumper harness cause I had issues in the past with crappy jumper harnesses

You should try the ECU in a different vehicle to see if the problem persists or if it specific to your vehicle.

ok will do ill let you kno as soon as I can get it swapped into another car and see what happends. thanks

What brand Jumper Harness? Even though it is brand new there could be a wiring mistake possibly in the jumper harness.