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Old 10-27-2007, 05:04 PM   #1
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Default help! Strangest problem ever???? WTF??

So today i put in a new heater core, no problem. After that i hooked up my 2nd o2 sensor (post cat). It was disconnected for a long time and i had a o2 SIM in place. But i still had a CEL for post o2 sen. Well the wires on the o2 were a bit beat up so i wrapped them up individually and then put them in some wiring loom.

Go to start the car and it starts and dies. Then i disconnect the o2 sensor at the harness up by the firewall/behind valvecover. This time the engine started right up but now my battery light is on....WTF?!?!?!

So i let th ecar run, turned on the lights/high beams/radio/ac/brakes or anything that might draw current. But nothing happens. Did it for like 15 but no difference and the car is idling at 2000rpms. So i took the car out on the street and it drove ok in vacuum. But slowing going into boost it starts cutting out/bucking. But if i floor the throttle, i see another 1psi then i normally do and the BATTERY LIGHT TURNS OFF UNDER BOOST!!!! But as soon as i let off the gas, the car bucks and the battery light comes back on. Drove the car around for about 10 min and nothing changed... batt light still on, low boost bucking, idle still at 2000rpms. And the whole time i was driving i had the lights on.

Anyone???
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Old 10-27-2007, 05:11 PM   #2
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Sounds like the secondary O2 is shorting the internal heater circuit to your O2 sensor wire or one of the wires is hooked up wrong. Disconnect it completely and see what changes.
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Old 10-27-2007, 05:24 PM   #3
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well, when i hooked up the rear o2, could it have mess up something else if it had a short?

I had something like that happen once, the rear o2 power wire grounded and it popped the engine fuse under the dash, but thats not what is happening this time.

But you're saying that i should disconnect the front o2 because i may have damaged it with the rear o2 possable being bad?
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Old 10-27-2007, 05:49 PM   #4
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The heater circuit inside the O2 sensor may be shorted to the sensor. I have seen this happen specifically on NGK O2 sensors. Disconnect the rear, since that is the one that you connected and started with the trouble if I am reading correctly.
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Old 10-27-2007, 06:06 PM   #5
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yeah, but i already disconnected the rear becasue the car would run when it was connected.
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Old 10-27-2007, 06:44 PM   #6
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Quote:
Originally Posted by DropTopDrifter View Post
yeah, but i already disconnected the rear becasue the car would run when it was connected.
You mean would not run?
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Old 10-27-2007, 10:19 PM   #7
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correct. the car would not stay runnning with the rear o2 connected
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Old 11-01-2007, 11:11 AM   #8
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Well, after pouring over wiring diagrams for a long time, and talking with the guys over at DIY, i have come to the conclusion that somehow or another the rear o2 sensor was hooked up wrong and sent a 12v signal back through the ground that all the sensors are on (4 sensors reading high input voltage to ECU). Im pretty sure the ECU is toast.... only other thing it could be is a short caused by the 12v surge..... but it didnt have it on long so hopefully that is not the case.
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