I've been fighting this problem for awhile now and i just can't figure it out. My civic has 104,500 miles on it and it studders under load in 1st and 2nd gears and every now and then in 3rd. I've checked my voltages at all of my sensors and they all check out fine and are within spec. Since it studders under load, i thought it might be a MAP sensor goin bad, but the voltage reads fine. about a month ago it set a check engine light and when it set the light my gas mileage took a major hit. the code was a code 41 (heater circuit malfunction on the O2). the check engine light wasn't letting the car go into closed loop. i changed the O2 sensor today but the car still studders like it did before. any of you guys have any ideas??

any help would be appretiated!!

Zac S