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98 Posts
Discussion Starter #1
Just put on my MVP header, it looks great and fits good too. When I first hit the road, it felt great, definetly more power, but after 5 miles it started hesitating like it was missing. Now it sounds like it's missing at an idle and the power is gone. Out of the 3 oxygen sensors, I removed the two in the factory header, since I was told by a local shop that they didnt' do anything on an OBD 1 car. Do I need to remove the rear sensor or replace the front two?

1994 NA
 

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Found E85 NOT in NJ!
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5,253 Posts
....are you sure that you are ODB 1? There is only two O2 sensors on a ODB1, right on top of the headers....there is no post cat o2 sensor

Somone correct me if I am wrong, because sometimes toyota does some tricky shit
 

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Master Yos
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2,215 Posts
obd1 only has two sensors put them back on the ecu is goin crazy that's why is acting up like that
 

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correct obd1 has 3, as stated earlier put back the two in the header, the ecu needs them, then pull the negative batt cable to reset the ecu.
 

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Now...Whitesupra94
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correct obd1 has 3, as stated earlier put back the two in the header, the ecu needs them, then pull the negative batt cable to reset the ecu.

maybe later year obdI has 3? I have a 93 MKIV, definately only has two. and you dont want to be removing either or them. They kinda tell your car how to run correctly....
 

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I think the Cali spec OBD1's have three sensors
 

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Master Yos
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well mine had 3 sensors obd2 i know obd1 only has 2 i do not know about cali spec who was the idiot that told you to take out the sensors
 

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Discussion Starter #10
Ok, put the sensors back in the header, running a lot better, but it is hesitating around 6,000 rpms. And the check engine light is throwing code 71. I still have the factory wires, and the plugs are NGK non-platinum with around 3000 miles. Any ideas?
 

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The Stars At Night
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1,460 Posts
First off, yes, non-Cali Supra's I can guarantee have only 2 O2 sensors. I put on my own turbo kit, I had to solder the two that were in the header together, then I replaced the rest of the exhaust to where it splits, so I know there is no post-cat O2 sensor.

Second, code 71 is the EGR. I was throwing that awhile after I installed the turbo. DaveH said something about the circuit heating up too fast. Anyway, there is a harness toward the back of the engine on the driver's side coming from the EGR. You want to disconnect it, take the side that leads towards the ECU, cut off the clip of the harness, and solder a resistor to the two wires. I can't remember exactly, but I think it was 10kohm 1/2 watt resistor? Can anyone confirm that?
 

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Found E85 NOT in NJ!
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yeah it is....daveh told me the same thing except i not cutting the harness off, rather just sticking it in there with some hot glue and some electrical tape
 
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