So I've been chasing this misfire code and my hesitation and lack of power when trying to accelerate heavy and it's slowly becoming better. To date it's been plugs, wires, fuel filter, cai cleaned along with mass air flow and intake/throttle body cleaned. Compression tested good across all cylinders and fuel pressure was good same with fpr. After all this it persists but now not every time I step on it. As well now I'm throwing a code for my 1st 02 Sensor saying bad switching. I was just curious if others have had similar experiences with 02 sensors wrecking havoc like this?

Also thanks to those on here who gave me idea in a previous post, helped a lot

 

Oyxgen sensors can affect fueling, and random misfires are usually fueling related. It's a good start

Also see if they can do a backpressure test on your cat. They are known problems

 

A couple of questions: Have you had an Engine running scan done on your car? Is it missing on all cylinder or just one or two?
If it's missing on all cylinders, you could have a bad Ignition Module. On just two cylinders, 1 & 4, 2 & 5 or 3 & 6, you could have a bad coil. If it is missing on one cylinder then it could be a bad plug or plug wire.
If when you try to accelerate the car bogs down you more than likely are miss firing on 2 cylinders off the same coil! As mentioned above. I think that is your problem. If your I.M. were bad your car would not run, or it would have no Power and you would have a smell of fuel in the exhaust.

 

The only code for misfire is just the p0300b random cylinder misfire. Idle and "normal" driving has zero issues and only ever has a problem when wanting performance out of the engine. I wasn't able to get a running scan done, too poor lol, but it's just been the p0300b and p1133b now is what I'm down to.

 

Have you checked for vacuum leaks? A lean mixture could cause both the codes you're getting.

 

So a little more information today. My issue definitely does not occur when the engine is cold. Was very cold here this morning and when I pulled onto the highway I had no misfire. It didn't occur until the car had warmed up and came out of open loop.

 

I think you should get that running scan done. It will definitely tell you what is wrong. I think your problem is Electrical because you have associated it with Engine Temperature!

 

Had it in at the shop today and everything tested good aside from the 02 Sensor and some whacked out af ratios they attributed to the 02 being messed. New 02 going in tomorrow and hopefully be the end of my woes lol

 

Be careful what brand they use. I like to recommend ACDelco or Denso

 

Denso is the only brand I was able to obtain today or would have been a few days to a week for a new one. I live in the middle of nowhere so you know lol