Hey guys, hoping you can help me narrow down the issue instead of shooting the parts cannon.
98 Tahoe, 4WD, 222k miles
Recently, I have noticed that I have been intermittingly been getting a misfire and pulled the info, finding mainly on cylinder 6 (initially ~300) and occasionally cylinder 5 (initially ~40) along with a code regarding the B2S1 O2 sensor (forget what code was - thought I screen shot it before clearing it). I ran some MMO in the gas tank and with an oil change (per instructions on the bottle). Later, I was driving up a decent and long grade at 65+ MPH and really noticed a misfire and started monitoring the data. The cylinder 6 misfire climbed to about 3000 and cylinder 5 to about 250. The road leveled off and the misfire went away. It seemed the harder I pushed the engine up the grade, the more prominent the misfire would get.
The code for the O2 sensor seems to have stayed away since initially seeing it. After the grade that really caused the misfire to be prominent, I have driven about 150 miles and no more codes/misfires.
I figure it is most likely a fuel delivery issue (I hear the CFI spider injection has its problems) or an ignition issue (I think I've read the ignition system can be a little finicky when starting to change parts there).
Any input on what the issue may be and additional info I can provide would be appreciated.
History - as far as I am aware, the truck still has the original CFI spider, distributor, cap, rotor, etc. Spark plugs were last changed at 180k miles. I got the truck with 176k miles and for the most part, had no issues. I am unsure of any maintenance down prior to getting it. The only major issue was in the first 150 miles of buying the truck and the transmission blew as I was towing a small trailer up a hill on the freeway, however when I got it towed to the shop and they replaced it, I was told it appeared as someone put gear oil in the transmission instead of ATF, causing the problem.
Thanks.
98 Tahoe, 4WD, 222k miles
Recently, I have noticed that I have been intermittingly been getting a misfire and pulled the info, finding mainly on cylinder 6 (initially ~300) and occasionally cylinder 5 (initially ~40) along with a code regarding the B2S1 O2 sensor (forget what code was - thought I screen shot it before clearing it). I ran some MMO in the gas tank and with an oil change (per instructions on the bottle). Later, I was driving up a decent and long grade at 65+ MPH and really noticed a misfire and started monitoring the data. The cylinder 6 misfire climbed to about 3000 and cylinder 5 to about 250. The road leveled off and the misfire went away. It seemed the harder I pushed the engine up the grade, the more prominent the misfire would get.
The code for the O2 sensor seems to have stayed away since initially seeing it. After the grade that really caused the misfire to be prominent, I have driven about 150 miles and no more codes/misfires.
I figure it is most likely a fuel delivery issue (I hear the CFI spider injection has its problems) or an ignition issue (I think I've read the ignition system can be a little finicky when starting to change parts there).
Any input on what the issue may be and additional info I can provide would be appreciated.
History - as far as I am aware, the truck still has the original CFI spider, distributor, cap, rotor, etc. Spark plugs were last changed at 180k miles. I got the truck with 176k miles and for the most part, had no issues. I am unsure of any maintenance down prior to getting it. The only major issue was in the first 150 miles of buying the truck and the transmission blew as I was towing a small trailer up a hill on the freeway, however when I got it towed to the shop and they replaced it, I was told it appeared as someone put gear oil in the transmission instead of ATF, causing the problem.
Thanks.
