Testing the O2 Sensor
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Testing the O2 Sensor
Does anyone know if I can test the O2 Sensor by driving my truck with the O2 Sensor unplugged from the wiring harness? I would need to drive it at least 20 miles to fully test if it is the cause of a surging problem my truck is having. Would that damage the engine or anything if I did that? Any ideas on it?
Thanks
Thanks
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Joined: Jun 2006
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From: Ottawa, Ontario
No.. you can't test the O2 sensor that way and you can't test it with a multimeter at all. If you unplug the O2 sensor the computer will run in open loop so that's not going to tell you anything either.
Is your motor surging all the time or just at idle?
Is your motor surging all the time or just at idle?
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it's surging at specific times. It will fluctuate at idle only on cold start after it has leveled out to it's normal idle. It will then start to bounce up and down from around 600 to 1000 rpms. it stops fluctuating when i put it into park or reverse. Then again on first cold drive when i get 8-20 miles down the highway it will start to surge (maybe hunting?) first 200 rmp jump then 400, 1000, and even higher. The higher it surges the more likely it is to jolt. I pull over, turn it off and back on and i can drive the rest of the day without one surge unless it cools for too long then I start back at the beginning of the whole cycle. Started the day my alternator went out and i put a new one in. So i'm suspecting the alternator fried a sensor somewhere.
I took it to ford yesterday and their mechanic couldn't find the cause. But he was looking for a vacuum leak or rodents and they said he didn't have the right tools to test anything. I think though it must be related to the electrical system because of the timing with the alternator failing.
I took it to ford yesterday and their mechanic couldn't find the cause. But he was looking for a vacuum leak or rodents and they said he didn't have the right tools to test anything. I think though it must be related to the electrical system because of the timing with the alternator failing.
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There was no codes.
I figured it was a bad alternator so replaced it with a salvaged one to test and still nothing changed.
I'm almost 100% sure it's fixed now though. Today I replaced the IAC for the surging at idle and it now idles great. Bought a new motorcraft alternator and put it in. And found that the negative cable to the battery was not connected well and the wires underneath looked corroded so I replaced the terminal and shined up both posts and terminals. Took it for a drive today twice when fully cold and no surges. It ran great. I think the terminals were bad and so it was lacking power and maybe when the torque converter would unlock it wouldn't be able to handle the lack of power and would start to try to compensate which would cause the big surges. I'll have to drive it a few more times to be sure its fixed. But i haven't been able to drive it like i did today without it surging .
I figured it was a bad alternator so replaced it with a salvaged one to test and still nothing changed.
I'm almost 100% sure it's fixed now though. Today I replaced the IAC for the surging at idle and it now idles great. Bought a new motorcraft alternator and put it in. And found that the negative cable to the battery was not connected well and the wires underneath looked corroded so I replaced the terminal and shined up both posts and terminals. Took it for a drive today twice when fully cold and no surges. It ran great. I think the terminals were bad and so it was lacking power and maybe when the torque converter would unlock it wouldn't be able to handle the lack of power and would start to try to compensate which would cause the big surges. I'll have to drive it a few more times to be sure its fixed. But i haven't been able to drive it like i did today without it surging .
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