OBX Header/ O2 problem
 

Last year I ordered the OBX headers which btw has a bung hole for the first O2 sensor to put in. I also ordered the CEL eliminator from RoadRace. At the time, i didn't know that the CEL eliminator was supposed to go on the second O2 sensor. So I had it put in on the first O2 sensor hole. A week after that, I found out it was on the wrong hole, so I got my mechanic to to take the spacer off and in doing so, it ended up breaking off. So basically, I had that hole plugged, and he made another bung hole just above the broken one and that is where my O2 sensor is in now.

Secondly, since the spacer was broken, I had the 2nd O2 sensor rerouted to AFTER the catylic converter

NOW --- I still get very BAD gas mileage on the car and the Check Engine Light is on. I got it read and it said:


P0171 - fuel system too lean in bank 1 (or something like that)

I know its a problem with the first O2 sensor. The second one I am assuming is perfectly fine.

Now is the problem the O2 sensor itself? Or is the problem with the new bung hole that was created for it? If I add a spacer for the O2 sensor, would that reverse the problem, or is the O2 sensor defective?

Thanks.

The first O2 sensor might be dead. Your car is 6 years old, I could easily see it wearing out and dying. I'm 99% sure you need a new front O2 sensor and the problems will all go away.

With your 2nd O2 sensor after the cat, you've totally solved the cat issue.

I ordered a front o2 sensor ... some sensor made by WALKER , about 100 bux off ebay. I will certianly try and replace it, however does it matter how far the o2 sensor plugs into the header? What if the sensor has to be further out. Couldn't that have been the reason it burned out in the first place?

^So are you asking does the height of the bung make the plug "go bad" quicker? thus allowing more of the sensor tip to sit the exhaust flow? I don't think it does...

what about if the oxygen sensor sits too far into the hole? is it possible the stock holes only let in a small amount of exhaust to the sensor?

On the stock manifold the sensor is fully into the exhaust stream. One possible problem (not sure if this applies I haven't seen the OBX header) if your OBX header is like the RPW header and they put the O2 sensor in one exhaust runner instead of in the collector, you could have a problem with just that one cylinder (fuel supply or ignition). However I would start with the O2 sensor as that is more likely.

ohh that actually makes a little sense... so if I basically get a new O2 sensor - and the problem still occurs, Ill jsut get another bung hole made bellow in the collector , where all the cylnder exhaust is at. Right now it's sitting in the 2nd or third exhaust runner... i can't remember right now. Thanks.

FIXED!!! O2 SENSOR NEEDED REPLACING. THANKS BLACKSHEEP

Selling my crap-lancer very soon.

!!!!!!!!!!!!!!!!!!!!! CHECK ENGINE LIGHT CAME ON AGAIN!!!!!

What can the problem be? I replaced O2 sensor. Do I have to relocate the O2 sensor? Or add a non-fouler or something to it to make it read less oxygen?

Just get the code for the CEL again and report back here.

i replaced spark plugs, and reset ecu . light is off... so lets see how long it lasts this time.

Look here!!!!!!!

https://www.evolutionm.net/forums/sh...=234344&page=3