pre o2 sensor exhaust leak

[dan2288]

I have a leak at the o2 housing to turbo. I was useing seafoam and found it. What effects would that have? I have a problem with getting knock at higher rpms and It just came out of nowhere. Just wondering if that can cause it ?

 

[delta448]

Exhaust leaks can make the sensor read lean or rich depending on the exhaust pressure. Usually lean at idle/low throttle/cruise and rich at higher load/boost. How lean or rich is tough to say but it will certainly screw with the fuel trims the longer it has to learn the wrong condition. If it's only at WOT or above 4k rpm, then it isn't just because of the O2 sensor since the car is in open loop and completely ignoring O2 feedback, but it might be related to the O2 sensor by way of the fuel trims. The way to test whether the fuel trims are causing the knock is to reset the ECU and immediately log a pull through the gears. If the knock is gone, then the long term fuel trims are probably causing the knock, if it's still there then look elsewhere for the cause of the knock.