Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
I hooked up a vacuum gauge due to a loss of power and misfire under high load. Engine has 200k vacuum gauge is 16inhg and steady leading me to late ignition timing. from my understanding the timing can't be adjusted on a COP system. Do I need to do a crank relearn or how do I fix this
They go full rich? As in close to 1 volt both banks?? If so I’d definitely pull the oxygen sensors out and check the exhaust back pressure with a back pressure gauge
I just had one doing exact thing. if you can get your hands on a back pressure gauge they will save you so much time This clearly sounds like a clogged catalytic converter. That back pressure gauge simply threads into the upstream o2 sensor port and you rev the engine. it should be easily on the green at idle and if it goes to red scale then you have a clogged Catalytic converter.
From what I remember these Cats are serviced as one unit and don't forget to get the new gaskets for both sides they never seal right when reused especially the driver side one which is a crush ring style but get both and save yourself the headache
