I raced in the Viper Vette circuit at Thompson two weeks ago and after a trial run the car was hard to hold at idle, it wanted to stall. When I brought it back and ran it on the street the idle was still terrible. After a short time the idle hang started happening, it would go up to 2000 and then on it own drop back to 700.
At this point I put the scan tool on the car and drove it, I found that one of the O2 sensors had a voltage of 1.5 volts at or near idle, that equates to an a/f ratio of close to 10 on that bank. I continued to monitor the O2 voltage and the short/long term adaptives. I also read the dagnostics manual where it relates to the O2 system, here are some observations and finding:
1. I replaced one O2 with a Bosch #13100 ($60 at NAPA), be careful there is a mistake in the Bosch cross reference, depending on which year the cross is it could give you another number.
2. The new O2 sensor stopped the idle issue and the idle hang problem.
3. The idle is now better then it has ever been, this O2 must have had issue for some time.
4. For some reason the O2 voltage on the bad sensor was only out of range at or near idle, if it deviated at othe rpms I didn't catch it.
5.The reason the idle was so bad was that the O2 sensor was showing 1.5 volts or extremely rich, therefore, the PCM was pulling fuel at idle, my aftermarket a/f gauge showed extremely lean because of the fuel being pulled.
6. A hard code was never set, probably I didn't run it long enough. They were soft codes set showing a rich condition, but, you wouldn't see them without a scan tool.
7. There are some gray comments in the diagnostics manual, but, what it seems to say is, a hard code won't be set unless the O2 voltage is over 1.5 volts. I sure there are other ways to set a over-rich code, but, strictly based on O2 voltage, they are looking at greater than 1.5 volts.
8. If you have a scan tool, the O2 voltage at 14.7 s .458 volts and the voltage should be in a plus/minus 0.2 volts.
9. Another interesting item is the fact that all the adaptives are purged when clearing the over-rich DTC. I am not sure whether this is all DTC's or just those dealing with a/f. I have a new (second) scan tool and it gave a warning (never seen on the old scan tool)that all adaptives were going to be purged with the clearing of the DTC.
10. The car has Ballangers and the O2 location is a little further from the male connector at the motor mount. I have to pull the male connector off of the mount to make it work originally. On my car the Ballangers also postion the the O2 sensor a little higher and closer to the the heat deflector. The O2 wires are uncomfortably close to the that plate.
The Bosch sensor is actually 1/4" higher than the NTK oem sensor, it might have worked, but, I didn't want the wires rubbing on the plate, so I used a hole saw to cut a hole where the sensor is positioned.
One last item, after this surging and idle hang episode it started me thinking about the number of SC and Turbo cars that have this problem. This may be a stretch, but, my car is proof that the O2's can cause the idle hang and surging. It is also the nature of the narrow band O2 sensor that it is not accurate under high pressure and/or high heat, in other words on high hp cars they shouldn't be as close to the engine as they are - is the idle hang problem as simple as a temporary malfunction of the O2?
At this point I put the scan tool on the car and drove it, I found that one of the O2 sensors had a voltage of 1.5 volts at or near idle, that equates to an a/f ratio of close to 10 on that bank. I continued to monitor the O2 voltage and the short/long term adaptives. I also read the dagnostics manual where it relates to the O2 system, here are some observations and finding:
1. I replaced one O2 with a Bosch #13100 ($60 at NAPA), be careful there is a mistake in the Bosch cross reference, depending on which year the cross is it could give you another number.
2. The new O2 sensor stopped the idle issue and the idle hang problem.
3. The idle is now better then it has ever been, this O2 must have had issue for some time.
4. For some reason the O2 voltage on the bad sensor was only out of range at or near idle, if it deviated at othe rpms I didn't catch it.
5.The reason the idle was so bad was that the O2 sensor was showing 1.5 volts or extremely rich, therefore, the PCM was pulling fuel at idle, my aftermarket a/f gauge showed extremely lean because of the fuel being pulled.
6. A hard code was never set, probably I didn't run it long enough. They were soft codes set showing a rich condition, but, you wouldn't see them without a scan tool.
7. There are some gray comments in the diagnostics manual, but, what it seems to say is, a hard code won't be set unless the O2 voltage is over 1.5 volts. I sure there are other ways to set a over-rich code, but, strictly based on O2 voltage, they are looking at greater than 1.5 volts.
8. If you have a scan tool, the O2 voltage at 14.7 s .458 volts and the voltage should be in a plus/minus 0.2 volts.
9. Another interesting item is the fact that all the adaptives are purged when clearing the over-rich DTC. I am not sure whether this is all DTC's or just those dealing with a/f. I have a new (second) scan tool and it gave a warning (never seen on the old scan tool)that all adaptives were going to be purged with the clearing of the DTC.
10. The car has Ballangers and the O2 location is a little further from the male connector at the motor mount. I have to pull the male connector off of the mount to make it work originally. On my car the Ballangers also postion the the O2 sensor a little higher and closer to the the heat deflector. The O2 wires are uncomfortably close to the that plate.
The Bosch sensor is actually 1/4" higher than the NTK oem sensor, it might have worked, but, I didn't want the wires rubbing on the plate, so I used a hole saw to cut a hole where the sensor is positioned.
One last item, after this surging and idle hang episode it started me thinking about the number of SC and Turbo cars that have this problem. This may be a stretch, but, my car is proof that the O2's can cause the idle hang and surging. It is also the nature of the narrow band O2 sensor that it is not accurate under high pressure and/or high heat, in other words on high hp cars they shouldn't be as close to the engine as they are - is the idle hang problem as simple as a temporary malfunction of the O2?
