My accord started to hesitate/shake a little, or sputter when starting to move from a stop when lightly on the throttle. It happend after removing the header and custom muffler and going back to stock. And a different o2
Could it be the o2 sensor even without a check engine light on? Or the oem muffler sounds like is has **** rattling inside. I know it needs to be replaced could this cause it.
Any ideas please or if this has ever happend to anyone. Mileage also down to about 375 per tank.

 

I'm hoping that you never used any rtv on the exhaust as this will foul your o2 sensor within a few miles as the rtv burns and melts over the o2 sensor. The first thing you should look for is an exhaust leak. If you find a leak and after fixing it, you should replace the o2 sensor. Exhaust leaks foul o2 sensors as well since the ecu will fuel foul the sensor since it adds too much fuel to try to compensate. You can use seafoam to search for an exhaust leak, if you don't know how to do that you can have a performance shop do it. Be careful using seafoam is it's possible to damage your motor if the car stalls while your adding the seafoam to the intake.

It's very easy to get an exhaust leak if you don't use new exhaust gaskets each time you open up your exhaust and if you don't gently torque each bolt in a crisscross pattern using several stages.

 

Maybe I will try the o2 first. No exhaust leaks and no rtv was used. Manifold tq'd to proper tq spec. Just getting annoying.

 

What brand of O2? And why did you change it?

 

bosch, and because the 02 cross threaded in the p.o.s header.

 

Did you do an ECU relearn after swapping the parts? If not the ECU may be trying to adjust to the changes you made as you are driving it.