How did I mess up O2 sensor?
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How did I mess up O2 sensor? ('94 LT1, 80k miles)
I changed plugs, thermostat, flushed coolant. Car starts fine but the left O2 reads low and reacts sluggishly. When the engine is warm the O2 reads below 0.1mV and PCM goes open loop and very rich on the left side.
- The left side plugs were fouled with rich AFR. I change the plugs again and notice one wire was damaged so I change all wires. I start the car with both data master and a volt meter hooked up. The left O2 works the same as before, and the AFR goes rich again. No wiring problem since PCM and volt meter read the same.
- I remove the O2 and it's covered in soot. I heat it with a propane torch and it reads between -200mV and 900mV. I put it back in the car and it starts at 200mV higher than before "blow-drying" but the voltage drops again when engine warms up.
So I fouled the sensor, but what's the root cause? I took the intake out for getting to the thermostat and started the car while flushing, so it may have ingested a drop or two coolant. How do I make sure I don't break the new ACDelco sensor I ordered?
Would this be a good idea before throwing in a new O2:
- Reset the PCM
- Disconnect the left O2 so the PCM stays in open loop
- Seafoam it and do a few hot runs to clean the engine
- Swap the left and right O2 to see that there's no other underlying problem
I changed plugs, thermostat, flushed coolant. Car starts fine but the left O2 reads low and reacts sluggishly. When the engine is warm the O2 reads below 0.1mV and PCM goes open loop and very rich on the left side.
- The left side plugs were fouled with rich AFR. I change the plugs again and notice one wire was damaged so I change all wires. I start the car with both data master and a volt meter hooked up. The left O2 works the same as before, and the AFR goes rich again. No wiring problem since PCM and volt meter read the same.
- I remove the O2 and it's covered in soot. I heat it with a propane torch and it reads between -200mV and 900mV. I put it back in the car and it starts at 200mV higher than before "blow-drying" but the voltage drops again when engine warms up.
So I fouled the sensor, but what's the root cause? I took the intake out for getting to the thermostat and started the car while flushing, so it may have ingested a drop or two coolant. How do I make sure I don't break the new ACDelco sensor I ordered?
Would this be a good idea before throwing in a new O2:
- Reset the PCM
- Disconnect the left O2 so the PCM stays in open loop
- Seafoam it and do a few hot runs to clean the engine
- Swap the left and right O2 to see that there's no other underlying problem
Last edited by t5mika; Nov 10, 2008 at 07:04 PM. Reason: .
