PO300 code

[ls1mike]

Yeah, but man it would have to be really bad to go instantly like that. I have had them get "lazy", but not die like that. That is an odd one. P0300 by itself is hard to troubleshoot. Especially when intermittent and no 02 sensor code.

Running rich

 

[xxch4osxx]

Originally Posted By: ls1mike
Yeah, but man it would have to be really bad to go instantly like that. I have had them get "lazy", but not die like that. That is an odd one. P0300 by itself is hard to troubleshoot. Especially when intermittent and no 02 sensor code.

Running rich
Thanks for that link, it is quite informative! Well, I am just going to buy an O2 sensor and see what happens. If that doesn't solve it, I will have to take it to the next level I guess.

 

[xxch4osxx]

Update: I replaced the pre-cat O2 sensor on that bank, and let it warm up to temp and no codes appeared. I took it out for a short drive and it ran perfectly. The O2 sensor was a real [censored] to get out and it was filthy, not just carbon, but hard crusty stuff, I'm guessing from the oil it burns from the leaky valve stem seals. I think I will be getting another O2 sensor for the other side and do it soon as well. They are all original.

 

[Tzu]

+1. I did this to my Impala 3800 and unplugging it made it run great. Replaced it and it runs like new. My '00 Silverado 5.3 just had a P0300 and (so far) it has been off since I replaced the original spark wires. A scan gauge showed I had 245 misfires on #1 &#6 cylinders and the rest had 0 misfires. All the plugs looked normal and clean after I inspected them. If one bank has problems, I would think an upstream O2 sensor could be faulty. Hope you can find the problem.
Originally Posted By: Trav
Try unplugging the MAF and start it. Post the results. You may have a bad MAF or a large vacuum hose has either come off or broken.

 

[xxch4osxx]

Originally Posted By: Tzu
+1. I did this to my Impala 3800 and unplugging it made it run great. Replaced it and it runs like new. My '00 Silverado 5.3 just had a P0300 and (so far) it has been off since I replaced the original spark wires. A scan gauge showed I had 245 misfires on #1 &#6 cylinders and the rest had 0 misfires. All the plugs looked normal and clean after I inspected them. If one bank has problems, I would think an upstream O2 sensor could be faulty. Hope you can find the problem.
Originally Posted By: Trav
Try unplugging the MAF and start it. Post the results. You may have a bad MAF or a large vacuum hose has either come off or broken.
Read the post above

 

[Trav]

I hope this works out for you, it sounds like your onto something, you did good replacing that O2 in any case even if the cat is bad.
As Mike said P300 can be a real pain especially with a flashing CEL.
Something let go and it was immediate and critical. There are enhanced codes a generic code reader will not read them, i would like to get the scan tool on this one and look at the fuel trims.

 

[ls1mike]

Good to hear.
Hope it stays that way.

Trav, No doubt. I would love to get my HP tuners on this truck!

 

[xxch4osxx]

Update: Drove to work and back, about 20 minutes one way and no codes came up. I checked when I got to work and when I got home. So far so good. I will be doing the other pre-cat O2 sensor in the near future as well. The sensor I bought was an NTK brand. From what I can tell NTK is a division of NGK. I was told NTK is a major OEM supplier.
LS1Mike, what is a HP tuner?

 

[xxch4osxx]

Just to let you all know, my truck is still running great and no codes or rough running! I am going to buy another O2 sensor today for the other side and replace it.