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Discussion Starter · #1 ·
Hello.. I was wondering if a faulty o2 sensor might make the car run rich?? I know our cars run rich to begin with, but would this aggrevate the situation???? I notice that my plugs usually have a healthy coating of soot on them, and Imagine it to be b/c of the run rich factor.... So WHERE is the O2 sensor on a4g vtec.. is it behind the heat sheild?? where would one locate the sensor, and how hard is it to swap out???

Thanks,
Andres

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1994 VTEC
Eibach Pro-kit, KYB AGX shocks, AEM CAI, AEM pullies, Thermal exhaust.
 

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Discussion Starter · #2 ·
Oh and are there more then ONE O2 sensor??

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1994 VTEC
Eibach Pro-kit, KYB AGX shocks, AEM CAI, AEM pullies, Thermal exhaust.
 

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For you there is one O2 sensor since you have OBDI. The sensor is located on the midpipe of the header/exhaust manifold. The easiset way for you to get it off is to first disconnect the O2 sensor harness and actually remove the header. Loosen the bolts connecting to the catalytic converter and the bolts on the head. From there, you can bring it down and use and O2 sensor socket(found at any autoparts store). Make sure you put some anitisieze when you replace the sensor and reassemble it in the opposite of assembling.
jake
 

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Two things:
- a FAULTY O2 will not operate properly and should throw an MIL
- a FOULED O2 will continue to oscillate (the ECU thinks it's OK) but will likely foul plugs

I doubt this is your problem, though, at least, I doubt this will fix your problem. It is a known fact that intake/exhaust modifications including (but not limited to) intake pipe/filter, manifold work, head work, header, and exhaust will caus the car to run rich. This is most likely due to the fact that we have MAP-based a/f controls (and not MAF or MAD or a MAP combo). When you use only a MAP to determine flow your volume/speed characteristics HAVE to be known. Change them (with the mods above) and you throw things off horribly.

It would appear that Honda ECUs compensate for this by running rich. Exactly why no one is sure, but this is known fact. I believe they also run rich to start with, stock.

Your best bet is to have your ECU reprogrammed by a reputable house or to get an A'pexi or Field a/f controller. No matter what you do, it should be accompanied by time on a dyno w/a wideband O2 or tuned by someone with access to a wideband O2. There's no other way to get the mixture set right.

Your O2 sensor could still be fouled, especially if you've run rich for a long time. A fouled O2 will run rich and running rich will foul an O2, completing the vicious circle (muahahahaha...)
 

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<font face="Verdana, Arial" size="2">Originally posted by marcucci:
Two things:
- a FAULTY O2 will not operate properly and should throw an MIL
- a FOULED O2 will continue to oscillate (the ECU thinks it's OK) but will likely foul plugs

I doubt this is your problem, though, at least, I doubt this will fix your problem. It is a known fact that intake/exhaust modifications including (but not limited to) intake pipe/filter, manifold work, head work, header, and exhaust will caus the car to run rich. This is most likely due to the fact that we have MAP-based a/f controls (and not MAF or MAD or a MAP combo). When you use only a MAP to determine flow your volume/speed characteristics HAVE to be known. Change them (with the mods above) and you throw things off horribly.

It would appear that Honda ECUs compensate for this by running rich. Exactly why no one is sure, but this is known fact. I believe they also run rich to start with, stock.

Your best bet is to have your ECU reprogrammed by a reputable house or to get an A'pexi or Field a/f controller. No matter what you do, it should be accompanied by time on a dyno w/a wideband O2 or tuned by someone with access to a wideband O2. There's no other way to get the mixture set right.

Your O2 sensor could still be fouled, especially if you've run rich for a long time. A fouled O2 will run rich and running rich will foul an O2, completing the vicious circle (muahahahaha...)
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hmm so running on a bad O2 sensor will in return screw up my plugs? hmm...I guess thats why it takes a while to start her up these days. I just got the 02 sensor replaced after driving on it bad for a year.
 

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Phamine, you actually took off your header to change the O2 sensor? I changed mine last month and I just did it when I had my car up on jackstands to change the oil. Also, I thought Id get the O2 socket but it didnt work worth a **** for me. I just used a 3/4 closed box wrench. Hope this helps.
 
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