CAMARO6 - View Single Post - Thoughts: Left bank misfires + bad cat and o2

seanblurr · 01-07-2020, 10:57 AM

I have been fighting some power issues the last few events and finally brought it to a trusted track friendly dealer. The car had a CEL, about a left side pre-cat o2 sensor. Mechanic says the CEL for the o2 was masking the real reason for the CEL, a left side cat had gone bad. In addition, the car showed 10x the amount of misfires on the left bank when compared to the right bank. For example, the car will record around 50-100 on average misfires over a given period, my left bank was averaging 1500.

When cold, no misfires were presenting themselves, which makes it near impossible for the mechanic to replicate the issue and log in real time the misfires. The car simply can not be driven hard enough.

The thought process is to replace the cat and potentially the o2 sensor, take it to an event and gauge any perceived power issues and monitor for a new CEL. If the issues are still present, or the CEL comes back on, re-log the car and check for a history of left bank misfires. Evaluate and diagnose from there.

I would think a misfire caused the cat/o2 issue, not the other way around. But I suppose it's easier to fix the known issues first.

What are you guys' thoughts on this? Anyone come across a similar issue?

01-07-2020, 10:57 AM	#1
seanblurr Drives: ZL1 1LE Join Date: Oct 2016 Location: California Posts: 1,297	Thoughts: Left bank misfires + bad cat and o2 I have been fighting some power issues the last few events and finally brought it to a trusted track friendly dealer. The car had a CEL, about a left side pre-cat o2 sensor. Mechanic says the CEL for the o2 was masking the real reason for the CEL, a left side cat had gone bad. In addition, the car showed 10x the amount of misfires on the left bank when compared to the right bank. For example, the car will record around 50-100 on average misfires over a given period, my left bank was averaging 1500. When cold, no misfires were presenting themselves, which makes it near impossible for the mechanic to replicate the issue and log in real time the misfires. The car simply can not be driven hard enough. The thought process is to replace the cat and potentially the o2 sensor, take it to an event and gauge any perceived power issues and monitor for a new CEL. If the issues are still present, or the CEL comes back on, re-log the car and check for a history of left bank misfires. Evaluate and diagnose from there. I would think a misfire caused the cat/o2 issue, not the other way around. But I suppose it's easier to fix the known issues first. What are you guys' thoughts on this? Anyone come across a similar issue? __________________