Suburban P0300 Misfire, Need Help Understanding Live Data

DanInTexas
Sat, 10 Apr 2021 16:28:30 +0000
Maintenance/Repairs

1999 GMC Suburban K1500 5.7L

Truck started running pretty rough all of a sudden and check engine came on. I splurged and got a good scan tool (been wanting one for awhile).

The code came back P0300 which is “Random Misfire”.

So in the past I would just start doing all the usual suspects, vacuum leak, plugs, wires etc. but I want to see if the live data from the scanner can offer some insight to someone with more experience reading the data before I throw parts at it.

So according to the data it looks like Bank 1 is running rich and Bank 2 is running lean. I believe it’s running rich cause I can smell the gas.

Now what I’m thinking is it might be a faulty O2 sensor, about 2 months ago the check engine came on for an O2 sensor and then like 2 days later it went away on it’s own and never came back. The live data for the O2 sensors seems to be consistent for both banks, front and back sensors, so I’m not too sure.

So anyways, I would appreciate some input here on what to look for in the live data to try to narrow this down before I just start throwing money and parts at it.

Thanks.

8 posts - 5 participants