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Engine Code P0303 and Oil on #3 Spark Plug (PICS INSIDE)
Hello all,
My 1997 Camaro Z28 with stock engine is running real rough. One day it set a P0160 code, 02 Sensor Circuit No Activity Detected Bank 2 Sensor 2. It didn't appear to affect how the engine was running so I cleared it. The "check engine soon" light stayed off for a while, but came back about a week later on a rainy day. This time the "check engine soon" light was blinking. It only blinked for a little while, but then stopped. I checked the codes when I got home and the codes were P0160 and P0300, random misfire detected.
The misfire is getting worse. Now the car misfires as soon as I start it up and doesn't stop. If I check codes while engine is running, I get P0303 now, misfire detected cylinder 3 and I no longer set P0160 anymore. The P0303 code turns back into P0300 when the engine is turned off.
I did some searching on this forum and tried some things this afternoon. I swapped the spark plugs, spark plug wires, and fuel injectors between cylinders 1 and 3. Engine still sets P0303. I can feel the misfire and it's getting worse. Every time, as soon as I start it up, it starts misfiring and sets P0303.
Any advice is welcome! What do you guys think? Was the P0160 code a warning or just a coincidence? Would a bad oxygen sensor or a bad Optispark pick on just one cylinder like this? Car has 170,000 miles and the motor is stock. The guy I bought the car from had it since 80,000 miles. He said he never had to replace Optispark or water pump while he had it.
Stock 1997 Camaro Z28
6-Speed Manual
170,000 miles
My OBDLink MX shows that long term fuel % trim for bank 2 is 3.12% while the long term fuel % trim for bank 1 is 0% and the short term fuel trims for both banks are 0%. I'm not sure what to make of this. Is this because of the P0160 code I set earlier?
PID Values from OBDLink MX while Running in Open Loop 1/3
PID Values from OBDLink MX while Running in Open Loop 2/3
PID Values from OBDLink MX while Running in Open Loop 3/3
PID Values from OBDLink MX while Running in Closed Loop 1/3
PID Values from OBDLink MX while Running in Closed Loop 2/3
PID Values from OBDLink MX while Running in Closed Loop 3/3
I hope this isn't too many photos! I just want to provide all the information I know! The following are additional screens from my OBDLink MX. Hopefully someone can see something in this data that I don't!
For P0160, you can find some "oxygen sensor simulators" that will always give the PCM a perfect reading to get rid of the code. As far as I'm concerned the rear sensors are just there to let you know if your catalytic converter is going bad (basically to fail you on inspection and give more money to GM). The rears have nothing to do with the fueling of the car. My car has gutted cats so I have the simulators to eliminate the code. It just plugs into the wiring harness on the car and you should wrap your actual O2 sensors plug in electrical tape and tuck away somewhere hidden.
For the misfire, do a leak down test when the engine is kinda warm. If you have an ALDL cable and laptop handy you can data log and really get some info. Also, how does the exhaust smell shortly after the misfire? You can take a multimeter and pulse out each injector to see if anything isn't right.
05-08-2016, 08:16 PM
Engine Code P0303 and Oil on #3 Spark Plug (PICS INSIDE) 
It just plugs into the wiring harness on the car and you should wrap your actual O2 sensors plug in electrical tape and tuck away somewhere hidden.