I know there is a front o2 sensor in the housing up front and one post cat, but there is another one in my down pipe. the person I bought it from must have cut it off, so all it is, is a sensor in the bung and the wires cut off.

I have a few dtc codes. One of them is a

P0139- O2 sensor 2, circuit slow, Response Bank 1

others are

P0401- Exhaust gas, Re circulation flow, Insufficient (came up after a megan test pipe was installed)
P0506- IAC, System Revolutions (Guessing the Seal is bad)
P0304- Cylinder 4 Misfire (plugged/faulty Injector?) this one also came up when I installed the walbro and injectors (see sig)


I will be taking this to the dealership later this week to see what the huge lump sum will be

 

A lot of aftermarket downpipes have a O2 bung in them for a wideband. Previous owner probably had a wideband in it and cut it off instead of getting a plug for the bung. That O2 shouldn't ever be connected to the ECU though, so it being cut off isn't the cause of any of your codes.

For your P401 check the EGR vacuum hoses on the back/bottom of the throttle body. You likely blew one of them off. Just adding a test pipe wouldn't have caused that code, but depending on your boost control/tune situation, it might have increased your boost which popped the hose off.

 

just to make sure, check and see if the post cat one is actually the secondary o2, the plug should go up into the body of the car. if it is then the one that is cut is most likely the a/f ratio sensor. it prolly got siezed in there and he couldnt remove so he just cut the wire.
one of the codes is because of the test pipe i believe.
did u get it retuned after installing the injectors? you are more than likely running super rich (depending on what the previous size injectors were)
might also want to check the install of the injectors and make sure its all seated correctly.

 

I got my car tuned right after I installed the injectors and test pipe, so that was my guess as well, that the injector is clogged not seated correctly. being seated not correctly would result in fuel being visible around that area though, right? I checked and there is nothing visible. Guess ill have to go in the freezing cold tomorrow and start taking her apart!

 

Okay, so is this o2 sensor code for the back or front though? Please help, thanks

 

It is the rear 02. Their is a patch to get rid of the code and not run the rear 02 but it is a pain. Also doesn't seem to work with all the roms.

Mikey

 

Could an exhaust leak make my rear o2 sensor act faulty? When I cold start my car, I have to give her some gas while cranking it a few times...

 

Possibly, but I don't think so. The entire point of the rear O2 is to see if the cat is doing anything. The ECU looks for a difference in the readings of the front and rear O2. If they are the same, it means the cat isn't doing anything (or isn't present) and you get the code. If they are different, it means the cat is there burning off unburned fuel.

https://www.evolutionm.net/forums/ev...ighlight=p0139

Give that a try, it works great for me with a test pipe. Did you check the EGR hoses i mentioned before too? Those being blown off would give you a decent vacuum leak and possibly be the cause of your slight starting issue.

 

yes, I did find a hose that was completely off. I plugged it back in and now my vacuum has gotten worse...