speedracer40

Having sputtering problems with rpms in 5 to 6K range with random misfire and CEL. This usually occurs at mid throttle after I have backed off accelerator. My OBD scan tool shows an PID on O2 sensor 1 of a non-fluctuating reading of -1.371 mA whenever this problem happens. I just had Mazda replace my engine several weeks ago. I have also installed a new Bosch O2 sensor, AEM CAI, BHR ignition coils. I was having this problem also before engine replacement.

My educated guess is either a tuning issue where the PCM is not allowed to go above -1.371 (prob related to Mazda trying to control fuel trim and gas mileage issues). a failing Catalytic converter clogged, or a core PCM problem/electrical problem.

Has anybody ever experienced this? This is driving me crazy. It feels like a clogged cat but could this cause the O2 sensor issue.

Any solutions much appreciated.

P.S. I called Bosch tech assist...they said their wideband O sensors should range from -2.0 mA to +2.5 mA.

wcs

iTrader: (2)

Right so ... first thing is I would still say its the Bosch O2 .... the stock O2 is a wideband O2 sensor and being around the forums for awhile I've not recalled anyone using anything else but a OEM O2 sensor for ECU pick ..... many of us of a secondary wideband for logging.

Could be a clogged cat as well.

How to check ... mmmmmmm
You can unplug the O2 sensor the car will fall back to Open Loop ... see if this funny thing goes away ...
(6000 rpm you are in Open Loop anyway ... .so I'm guessing this won't change anything but meh we are in diagnosing mode, right? Don't want to just throw money aimlessly at new parts)

Check the cat to make sure it isn't a) Glowing red hot or B) Physically look inside and check