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Discussion Starter · #1 ·
Ok, here's a new one. Again, this is a 1990 MX6 DX. While working under the hood, I noticed the wire that comes from the sensor that is screwed into the exhaust header is running between the heat sheild and what I assume is the header itself. The wire seems to be trapped in there as I cannot slide it out the bottom of the heat sheild. I also notice the wire has a metal hanger that is just dangling off of it. I also notice a bolt hole through the heat sheild and into the manifold in the area where the hanger is dangling from the wire.

I assume this wire should not be pinched between the heat sheild and the header, but should run outside the heat sheild and be supported by the disconected hanger which should be bolted into the manifold. Am I correct? I wonder how the little wire has stood up to all that heat???

Thanks once again.
 
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That wire is for your Oxygen sensor. Chances are, it hasn't stood up to that heat and your car is running in whats called "closed loop" mode.

Basicly, the ECU is using preset values to know how much fuel to inject. You may notice a lot better gas milage if you replace the O2 Sensor and wire, and route the proper way (Your guess is correct).
 

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FlySwat said:
That wire is for your Oxygen sensor. Chances are, it hasn't stood up to that heat and your car is running in whats called "closed loop" mode.
...if the wire was severed, it would be "open loop" mode due to the lack of feedback from the o2 sensor. "closed loop" means that the control system (the ECU) is receiving a signal from the o2 sensor and functioning normally.

From what he says, it sounds like it's OK. If the wire is still intact, just take the heat shield off and make use of the mounting bracket. Most likely someone took the heat sheild off before and didn't bother to put the hanger back on.
 
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magik8 said:
...if the wire was severed, it would be "open loop" mode due to the lack of feedback from the o2 sensor. "closed loop" means that the control system (the ECU) is receiving a signal from the o2 sensor and functioning normally.
Dammit, I wasn't sure if I was mixing up the two when I wrote it, but I knew if I was wrong you would come in and correct me :)
 

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Discussion Starter · #5 ·
Thanks again guys. I hope I'm not being too big of a pain with all these questions. You are saving me time and money in most cases and adding to the saftey of my son's car in those where I end up spending on "unexpected" problems due to your advice.
 

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FlySwat said:
Dammit, I wasn't sure if I was mixing up the two when I wrote it, but I knew if I was wrong you would come in and correct me :)
just think of it as closed (circuit) loop, and open (circuit) loop
 

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Discussion Starter · #7 ·
Follow up question(s)

So I fished the wire out from between the sheild and header and found that the insulation was burnt off, exposing a white, inner inulation that was also burnt off at one small location. The wire underneath was still intact. I wrapped it with tape and properly mounted the bracket. The car started fine and the check engine light went right out when it started. I drove it around for about 15 minutes and the light didn't come on. Does this mean the thing is still working? Should I replace it anyway?

Thanks again.
 

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O2 sensor

If the internal wire wasn't damaged, it may be ok. This is one of those problems where a service manual comes in handy. There is a voltage test that can be performed by unplugging the sensor's connector and probing with a meter, while running the motor at various RPM's.
If you were getting a fault code before and it went away, my thoughts would be that its ok. It's best to clear the codes after any repairs. This is done by removing the battery's negative terminal and applying the brake pedal for a minute or so.
 

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Discussion Starter · #9 ·
Re: O2 sensor

johniebgoode said:
If the internal wire wasn't damaged, it may be ok. This is one of those problems where a service manual comes in handy. There is a voltage test that can be performed by unplugging the sensor's connector and probing with a meter, while running the motor at various RPM's.
If you were getting a fault code before and it went away, my thoughts would be that its ok. It's best to clear the codes after any repairs. This is done by removing the battery's negative terminal and applying the brake pedal for a minute or so.
Thanks.

I read about the test last night, but I don't have the equipment. I was not getting a light before or after. Is that method of clearing the codes the same thing you do to reset the ECU?
 

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yes its the same thing as reseting the ECU, He left one thing out though. so I'll give you every step including the ones he got right.
Dissconnect the neg. battary cable, then reconnect it. Get in your car and hold the brake for at least 30sec's. After 30sec's of holding the brake, start the car and let it idle for at least 1 min. During this time do not touch anything especially the accelator. The reason why you let it idle for a minute is so the ECU can read through all of the sensors and everything that the ECU relys on to give the correct amount of fuel.
Do you know how to pull ECU codes? if so try and see if you can pull any codes after the ECU is reseted, if you don't pull any codes (especially the O2 sensor code) then chances are that the O2 sensor wire is fine, and the ECU is getting a correct reading from the O2 sensor. If you do pull the O2 sensor code, replace the O2 sensor and the wire (the wire will usually come with the O2 sensor). Just FYI... if you go to the delear for a new O2 sensor they will expect you to pay apx. $200 for one. Go aftermarket, as a new aftermarket (uinversal) O2 sensor will only cost apx. $40 and it will work just as well.

If you don't know how to pull the codes read the FAQ on this site it will tell you excatly how to do it.
In short this is what you do.... You get a jumper wire and find a good ground to connect one end of the jumper wire to (IE: a bolt going into the firewall), the other end of the jumper wire plugs into the green connector (the connector is near the drivers side strut tower). Once you have it pluged into the connector turn the key on (or you can start the car). if there are any fult codes the check engine light will flash the code at you. a full second puse is the hundred place the 1/2 second pauses are equal to the tens place. For example: 2 full second pauses flowed by three 1/2 second pauses is equal to code 23. To interpet these codes into what they are. you need to find the list on this site or go to performanceprobe.com and the list will be on that site also. If you can't find the list I can E-mail it to you...just PM me if you need it. For example: code 05 (five 1/2 second pauses) is the knock sensor.

Hope this helps you a bit.

Methman

PS: If I were you Id replace the O2 sensor & wire anyway. Because the O2 sensor wire is sheilded, and if this sheild is broken it can distrupt the signal going to the ECU big time. This means that the car could be in open loop and running pretty rich. If its the origonal O2 sensor, it probley needs to be replaced anyway.
 
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