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Hey all, wasn't sure where to put this really so trying here. It's kind of a tech question, but more related to performance and tuning 'cause it's the result of modifications I made. I've been having problems with my O2 sensor fouling up for some time now and I'm trying to fix it once and for all. I've tried a few things and have some theories on more things I can try, but if anyone has any better ideas all input is appreciated. First the symptoms...
The switching of the sensors voltage reading from high to low starts slowing down and decreasing in range (from 500mv in the middle) at around 2000 miles after installing a new sensor. By 4000 miles I'm getting codes in the pcm for O2 sensor insufficient activity and SES light on. By then the car doesn't want to stay running when I start it without me playing with the throttle a little and it hunts around for idle and surges. My wideband O2 typically starts seeing AFR's in the 16:1 range at this point, so it's obvious the stock narrow band is fouled and the pcm isn't reading and adjusting fuel properly in closed loop.
Basically I think it could be related to two things. Either burning oil, or unburnt fuel going out the exhaust. Reason I think it could be oil is because I've read that boosted cars tend to have more airflow going out the valve cover into the PCV system than average due to the higher combustion pressures and resulting increase in blow by into the crank case. I installed a catch can in the PCV line because of this, but it doesn't appear to be working. The engine is usually about 1/4-1/2 quart low on oil after 4-5k miles, and the catch can hardly has any significant amount of oil in it. I'm still observing oil residue in the outlet hose and the intake manifold as well. I'm thinking the air is moving fast enough through the catch can at high throttle that the oil mist stays suspended in the air and goes right through. Any ideas on how to stop that oil there and let the other blow by gases pass through? I'd like to keep the PCV system intact with suction on it like stock to evacuate the crank case a low throttle since thats the majority of driving I do, rather than just using a valve cover breather. I've been thinking about maybe putting some kind of filter inside the catch can on the outlet side to stop the oil? Or maybe using some type of oil/water separator like for air compressors? Anyone else have experience with similar problems?
The other possibility of unburnt fuel, I'm addressing right now. I read that higher lift and duration cams actually slow down air velocity in the intake ports when at low rpm and can affect fuel atomization. This problem basically started after my major overhaul when I added the cam, injectors, and deleted the EGR all at the same time... so I figured that might be related. Obviously I don't want to take the cam out and I don't want to re-install the EGR. Scans have shown the injector pulse width doesn't get that high even at WOT redline, so I'm pretty sure they are bigger than I need. They are 42lb disc type injectors that have a jet pattern instead of a mist too... great for high rpm power and a really high injector duty cycle limit, but not so great for fuel atomization at idle. I picked up a set of 36lb GTP injectors that I think should be plenty for how much boost I'm running and hopefully with help with the idle. I'm also using one range colder plugs and a 180 thermostat. The plugs don't look fouled, but with my extra cooling capacity the car will actually run at 180 when the weather is cool. I've heard that engine and coolant temp can affect the combustion efficiency as well, so I'm wondering if that could be part of it? I don't think I really need to run as low as 180, and I have a stock 195 T-stat I can put back in. Basically I'm just trying to make sure I'm getting a complete burn.
The only other thing I'm changing is my wideband O2. Innovate motorsports contacted me with an offer they were doing for LM-1 owners where they'd let you turn in your used LM-1 and get $100 credit towards a new LM-2. Apparently they are going to give the LM-1's to tech schools and university automotive programs for classroom use. Anyway the LM-2 has a lot more features so I went ahead and got one. It's a full OBD2/CAN scan tool and code reader as well, and has more inputs/outputs than the old LM-1. I can still use one analog output for logging with my powertuner, and it has another one that's setup from the factory to simulate a factory narrow band output. I'm thinking about trying out hooking that up to the signal wire for the factory O2 and seeing if the engine will run better off of that. I'll have to turn off the DTC codes in the PCM for the stock O2 heater, but otherwise if it works I'm hoping it has an easier time maintaining the proper AFR. If it doesn't work I can always put the stock sensor back in. I'm getting tired of buying a new $60+ sensor every 4k though, so hopefully I can solve this once and for all.
The switching of the sensors voltage reading from high to low starts slowing down and decreasing in range (from 500mv in the middle) at around 2000 miles after installing a new sensor. By 4000 miles I'm getting codes in the pcm for O2 sensor insufficient activity and SES light on. By then the car doesn't want to stay running when I start it without me playing with the throttle a little and it hunts around for idle and surges. My wideband O2 typically starts seeing AFR's in the 16:1 range at this point, so it's obvious the stock narrow band is fouled and the pcm isn't reading and adjusting fuel properly in closed loop.
Basically I think it could be related to two things. Either burning oil, or unburnt fuel going out the exhaust. Reason I think it could be oil is because I've read that boosted cars tend to have more airflow going out the valve cover into the PCV system than average due to the higher combustion pressures and resulting increase in blow by into the crank case. I installed a catch can in the PCV line because of this, but it doesn't appear to be working. The engine is usually about 1/4-1/2 quart low on oil after 4-5k miles, and the catch can hardly has any significant amount of oil in it. I'm still observing oil residue in the outlet hose and the intake manifold as well. I'm thinking the air is moving fast enough through the catch can at high throttle that the oil mist stays suspended in the air and goes right through. Any ideas on how to stop that oil there and let the other blow by gases pass through? I'd like to keep the PCV system intact with suction on it like stock to evacuate the crank case a low throttle since thats the majority of driving I do, rather than just using a valve cover breather. I've been thinking about maybe putting some kind of filter inside the catch can on the outlet side to stop the oil? Or maybe using some type of oil/water separator like for air compressors? Anyone else have experience with similar problems?
The other possibility of unburnt fuel, I'm addressing right now. I read that higher lift and duration cams actually slow down air velocity in the intake ports when at low rpm and can affect fuel atomization. This problem basically started after my major overhaul when I added the cam, injectors, and deleted the EGR all at the same time... so I figured that might be related. Obviously I don't want to take the cam out and I don't want to re-install the EGR. Scans have shown the injector pulse width doesn't get that high even at WOT redline, so I'm pretty sure they are bigger than I need. They are 42lb disc type injectors that have a jet pattern instead of a mist too... great for high rpm power and a really high injector duty cycle limit, but not so great for fuel atomization at idle. I picked up a set of 36lb GTP injectors that I think should be plenty for how much boost I'm running and hopefully with help with the idle. I'm also using one range colder plugs and a 180 thermostat. The plugs don't look fouled, but with my extra cooling capacity the car will actually run at 180 when the weather is cool. I've heard that engine and coolant temp can affect the combustion efficiency as well, so I'm wondering if that could be part of it? I don't think I really need to run as low as 180, and I have a stock 195 T-stat I can put back in. Basically I'm just trying to make sure I'm getting a complete burn.
The only other thing I'm changing is my wideband O2. Innovate motorsports contacted me with an offer they were doing for LM-1 owners where they'd let you turn in your used LM-1 and get $100 credit towards a new LM-2. Apparently they are going to give the LM-1's to tech schools and university automotive programs for classroom use. Anyway the LM-2 has a lot more features so I went ahead and got one. It's a full OBD2/CAN scan tool and code reader as well, and has more inputs/outputs than the old LM-1. I can still use one analog output for logging with my powertuner, and it has another one that's setup from the factory to simulate a factory narrow band output. I'm thinking about trying out hooking that up to the signal wire for the factory O2 and seeing if the engine will run better off of that. I'll have to turn off the DTC codes in the PCM for the stock O2 heater, but otherwise if it works I'm hoping it has an easier time maintaining the proper AFR. If it doesn't work I can always put the stock sensor back in. I'm getting tired of buying a new $60+ sensor every 4k though, so hopefully I can solve this once and for all.
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