O2 sensor failure and effect on Cat.
Thread Starter
Racer
Joined: Mar 2005
Posts: 399
Likes: 2
From: Newtown PA
O2 sensor failure and effect on Cat.
I have a 95 LT1 6 speed with 54,000 miles. The engine has the typical LT1 oil leak at the front of the motor, the origin of which has been reported in this forum.
In any case, the right O2 sensor located before the converter failed at 26,000 miles (about 6 years ago). The failure occurred while driving to work and made itself known by a slight miss in the engine coupled with that rich mix/cat smell from the exhaust. I confirmed the failure with a scanner and some other tests and replaced it with a unit that I purchased from my local Chev dealor. During replacement, I referred to the factory service manual and noted that the sensor is a semiconductor that operates by comparing the O2 in ambient air taken into the sensor by the connector to the O2 in the exhaust. From this I surmised that since the connector of my failed sensor was soaked with oil, oil had entered the sensor, causing it to fail. I also figured that since the first sensor took 26,000 miles to fail, the second one would last that long too. So no big deal. And, therefore, I'm not going to take the time to fix the oil leak.
The same sensor failed last year at 52,000 miles presumably because of the oil leak. The connector on this sensor was also soaked with oil. I replaced this sensor with a Bosch unit purchased from Pep Boys.
Yesterday, on my way to Englishtown to do a little drag racing, the Bosch sensor I replaced last year failed. This sensor lasted 2000 miles. Unfortunately, I was already a half hour from my house. The car started missing and stinking bad with black smoke coming out the right exhaust. I had to drive the car about a half hour like that to get home.
According to threads posted in this forum, the Bosch O2s are lousy. I presume that this is why the third sensor failed so soon. The car does not leak anymore oil today than it did in 1995, when I purchased it. So I dont think that the Bosch sensor was subjected to more oil than the first two OEM units. Also, the connector does not seem that wet with oil. Just a little greasy.
I did note in this forum that the right O2 sensor located before the right cat. apparently fails repeatedly as compared with the left O2 sensor. I believe that the front oil leak common to the LT1 is the cause of this.
My question is: how much abuse can the right Cat. handle as a result of misfires caused by the overly rich mixture resulting from the failed O2 sensor. The first time the O2 sensor failed, I drove the car maybe a half hour and after replacement, I did not really perceive a no noticeable change in performance. The second time it failed, I noticed it in my driveway, and immediately stopped driving the car until I replaced it. Yesterday, I drove the car almost an hour before I got it home, and because it was so damn hot, the engine was missing real bad and a lot of black smoke was coming from the right exhaust pipe. I have not replaced the sensor yet, but I am expecting bad news from the Cat.
Note, that one reason I was taking the car to the dragstrip yesterday was to determine if the performance had dropped off. When I first bought the car, I took it to E-town a couple of times and it ran 13.7-13.8s at around 102-106. In past couple of years, I think I have noticed a loss of performance. I have always suspected that right Cat might be the cause of it. (I dont believe the Optispark is the cause of this perf loss, because when the sensor is operating, the engine runs smoothly and does not stall or hesitate, etc. It just doesnt seem to have the same edge to it.)
If anybody is still awake after reading this, please share your thoughts.
In any case, the right O2 sensor located before the converter failed at 26,000 miles (about 6 years ago). The failure occurred while driving to work and made itself known by a slight miss in the engine coupled with that rich mix/cat smell from the exhaust. I confirmed the failure with a scanner and some other tests and replaced it with a unit that I purchased from my local Chev dealor. During replacement, I referred to the factory service manual and noted that the sensor is a semiconductor that operates by comparing the O2 in ambient air taken into the sensor by the connector to the O2 in the exhaust. From this I surmised that since the connector of my failed sensor was soaked with oil, oil had entered the sensor, causing it to fail. I also figured that since the first sensor took 26,000 miles to fail, the second one would last that long too. So no big deal. And, therefore, I'm not going to take the time to fix the oil leak.
The same sensor failed last year at 52,000 miles presumably because of the oil leak. The connector on this sensor was also soaked with oil. I replaced this sensor with a Bosch unit purchased from Pep Boys.
Yesterday, on my way to Englishtown to do a little drag racing, the Bosch sensor I replaced last year failed. This sensor lasted 2000 miles. Unfortunately, I was already a half hour from my house. The car started missing and stinking bad with black smoke coming out the right exhaust. I had to drive the car about a half hour like that to get home.
According to threads posted in this forum, the Bosch O2s are lousy. I presume that this is why the third sensor failed so soon. The car does not leak anymore oil today than it did in 1995, when I purchased it. So I dont think that the Bosch sensor was subjected to more oil than the first two OEM units. Also, the connector does not seem that wet with oil. Just a little greasy.
I did note in this forum that the right O2 sensor located before the right cat. apparently fails repeatedly as compared with the left O2 sensor. I believe that the front oil leak common to the LT1 is the cause of this.
My question is: how much abuse can the right Cat. handle as a result of misfires caused by the overly rich mixture resulting from the failed O2 sensor. The first time the O2 sensor failed, I drove the car maybe a half hour and after replacement, I did not really perceive a no noticeable change in performance. The second time it failed, I noticed it in my driveway, and immediately stopped driving the car until I replaced it. Yesterday, I drove the car almost an hour before I got it home, and because it was so damn hot, the engine was missing real bad and a lot of black smoke was coming from the right exhaust pipe. I have not replaced the sensor yet, but I am expecting bad news from the Cat.
Note, that one reason I was taking the car to the dragstrip yesterday was to determine if the performance had dropped off. When I first bought the car, I took it to E-town a couple of times and it ran 13.7-13.8s at around 102-106. In past couple of years, I think I have noticed a loss of performance. I have always suspected that right Cat might be the cause of it. (I dont believe the Optispark is the cause of this perf loss, because when the sensor is operating, the engine runs smoothly and does not stall or hesitate, etc. It just doesnt seem to have the same edge to it.)
If anybody is still awake after reading this, please share your thoughts.
