My car recently developed a misfire, and shortly afterward it threw a PO133 code. I cleared the code about 70 miles ago and it has not come back, but the misfire is still there.

Both front O2 sensors are brand new (less than 200 miles) and it's my understanding that PO133 is "Bank 1 Sensor 1 -- O2 sensor slow to respond". I thought a misfire would throw a "low voltage" code and not a "slow to respond" code? although I'm not really sure

If PO133 can trigger from a misfire, then I know to start looking at the driver's side plugs/wires for a problem.

Any input on this is greatly appreciated!

Thanks,
Thomas.

 

Wow, no information at all on a PO133 code?
Anyone know of a website where I can look codes up?

Thomas.

 

"Misfires" set a "misfire" code - P0300. Not sure what you mean by a "low voltage" code.

A "slow" O2 sensor might give faulty feedback to the PCM and throw the long term fuel corrections off, leading indirectly to a misfire. Could even foul the plugs, but all that is just a guess. A scan would tell you which cylinder is misfiring, perhaps pointing you to the correct problem.

When you installed the new O2 sensors, is there any chance you contaminated them? When you get a "slow response" code, its usually the sensor.

 

Thanks for the info Injuneer. That's interesting you mention throwing the long term fuel trims off. I just posted in the Computer Diagnostics forum asking about the fuel trim. here is my post.

The low voltage codes (I had two of them, one for each sensor on bank 1) appeared when the misfire 1st started.
When I replaced the factory Y pipe with the RT Y pipe, I installed new front O2s, and also replaced the driver's side manifold gasket. Due to the manifold resting on the plugs for a bit, I figured I cracked one of them when changing the manifold gasket and it was misfiring causing both O2s in bank one to give a fault code. I replaced all plugs on the drivers side, cleared the codes, and they didn't come back. I then replaced the plugs on the passenger's side and took it to the track. When driving home from the track, the PO133 showed up.

I don't know what the long term fuel trim values should be, so I don't know if the values I'm seeing in EFI Live are indicating a problem.

When I ran the 1/4 with EFI monitoring, it didn't pick up any misfires. Even at idle, it doesn't show any misfires. The reason I think I have a misfire is because the car shakes pretty bad at idle, at part throttle it feels like it's missing on 1 or more cylinders (sluggish, lurching, etc ...), but when the throttle goes to 70% or so (guessing on the %), it wakes right up and acts normal.

I suppose there is a chance I could have contaminated the sensor, but I remember being very careful with them, and didn't even open the plastic until I was ready to thread it in. I suppose I could swap Sensor 1 on both banks and see if the code comes back. Although, I cleared the code about 100 or so miles ago and it hasn't returned; but the miss (or whatever it is) is still present.

Could the long term fuel trims be causing the car to act as though there is a misfire?

Thanks again,
Thomas.

 

I know this thread is pretty old but im having the exact same problem with my new 383 lt1. Car shakes pretty bad at idle, its like a sex toy. I havn't replaced the o2's yet but it shakes even in open loop and when it gets to closed loop it gets far worse. Would O2's cause the car to act up even in open loop? It sputters and hesitates a little bit when cold but when its warm it does it very often and consistent. Feels like 2 cylinders are off.