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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / February 2005O2 Sensor-2001 Galant-HELP!!
Ok, here's the story. My service engine light came on and the car started hesitating when I would accelerate. Had a mechanic read the code and he said my pre-cat O2 sensor is shot. Replaced the part myself and drove about 120 miles the next day. Car was running great and no engine light. The next day I start the car and the engine light is back along with the sluggish performance. 72,000 miles on the car. Any ideas folks?? What would be causing the light to keep coming on?? I can't believe a brand new sensor would be the problem. Thanks in advance.. >Ok, here's the story. My service engine light came on and the car >started hesitating when I would accelerate. Had a mechanic read the [quoted text clipped - 7 lines] > >Thanks in advance.. You have to check for corrosion at the plugs in the wiring harness for the O2 sensor, to be sure there isn't any. You may also want to take the "new" O2 sensor out and inspect it for fouling. If it is fouled, you have another different problem that is going to continue fouling your O2 sensors. The sooner you know about that the better. Next, maybe you should monitor that O2 sensor to be sure the voltages are going hi and lo enough. Should go up to zero point 9 volts, and drop to zero point 1, at a pretty good rate of speed ( every few seconds ) on a running engine. For some reason you're not getting the correct voltages to the PCM in the right time intervals to keep from throwing an O2 DTC code. It -could- be something in the exhaust manifold fouling the sensor, that is why you want to pull it and inspect it for fouling. If it is covered with crud, suspect a head gasket problem or similar. Lg > >Ok, here's the story. My service engine light came on and the car > >started hesitating when I would accelerate. Had a mechanic read the [quoted text clipped - 28 lines] > > Lg Thanks. I will pull it out and check it. What am I looking for exactly with "fouling"?? Am I just seeing if it has turned black or looks clogged? >> >Ok, here's the story. My service engine light came on and the car >> >started hesitating when I would accelerate. Had a mechanic read the [quoted text clipped - 36 lines] >with "fouling"?? Am I just seeing if it has turned black or looks >clogged? Sure. It should be _clean_, as in, the temperatures in the exhaust manifold where O2 sensor is located should reach up to 1,500Farenheit. That would normally burn-off anything except the most egregious kind of crud being spewed from the engine. If you see gunk, crud on your "new" sensor, there is something leaking into the exhaust manifold that is depositing that crud, either from the cylinders or from a leaking head gasket. As I said, at those temperatures, the O2 sensor should be -clean-. Were it not so, they would all foul and have to be replaced weekly if not daily. Lg I'm no expert, but I think an engine running rich can cause the computer to throw the 02 sensor code. Mark > I'm no expert, but I think an engine running rich can cause the computer > to throw the 02 sensor code. > > Mark I'm a total novice so what does "running rich" mean? Is there something I can do to fix that? >> I'm no expert, but I think an engine running rich can cause the >computer [quoted text clipped - 4 lines] >I'm a total novice so what does "running rich" mean? Is there something >I can do to fix that? Some of the feedback for rich/lean comes from the O2 sensor. When the mix goes rich ( too much unburned fuel in the exhaust relative to the O2 content ) the voltage of the O2 sensor goes low. Too little unburned fuel to O2 ratio, the sensor voltage goes high. If the mix is rich, you can thank, in part, a defective O2 sensor for that. The most likely problem here is corroded contacts at the O2 sensor plug, but you must leave this connector unmolested. Do not block off it's plug in any way, as that is where the O2 from the atmosphere enters the sensor, and if you put goop there, it will choke the sensor off. So if the engine is running rich, the O2 sensor itself is suspect. Either it isn't toggling quickly enough according to the algorithm in the PCM module, or it isn't reaching the required hi/lo voltages required for proper signal recognition. Time and amplitude are what you're looking at here. A defective O2 sensor can cause a too rich mix. It can also cause a too lean mix if it sticks hi. If you don't have the equipment or experience to work through this problem, you'll have to bring it to a qualified tech. Lg > When the mix goes rich ( too much unburned fuel in the exhaust relative to the > O2 content ) the voltage of the O2 sensor goes low. Too little > unburned fuel to O2 ratio, the sensor voltage goes high. You have it backwards. >> When the mix goes rich ( too much unburned fuel in the exhaust relative to the >> O2 content ) the voltage of the O2 sensor goes low. Too little >> unburned fuel to O2 ratio, the sensor voltage goes high. > >You have it backwards. Hi O2 in exhaust causes sensor voltage to drop to 0.1 Lo O2 in exhaust causes sensor voltage to kick up to 0.9 this I have noticed and recorded. It is a matter of record. Otoh, fuel, I didn't monitor that. It is always opposites. See above. Lg >> When the mix goes rich ( too much unburned fuel in the exhaust relative to the >> O2 content ) the voltage of the O2 sensor goes low. Too little >> unburned fuel to O2 ratio, the sensor voltage goes high. > >You have it backwards. oops ur right |
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