Ok I'm working on a 03 DII with 66,692 miles.

Back in March of 2007 ( 57,942 miles) it had the plugs (Champion) and wires (STI wires) replaced by dealer along with the 60k mile service.

Now its throwing some codes.

P0150 O2 sensor circuit malfunction (bank 2, sensor 1) or Front sensor RH bank stoichiometric ratio outside operating band

P0174 System too rich (bank 2)or Multiplication injector adaptive fuelling - rich limit exceeded RH bank

A month ago I cleaned the throttle body and did seafoam treatment. At the same time I retrieved some misfire codes (but I don't remember them)

He then tells me that he has noticed a black ring around his tail pipe


And when he puts his hand at the end of the pipe, his hands get like this



So....
Yesterday I went and removed his front right O2 Sensor and replaced it with mine. (hence this thread) O2 Sensors Look Good??
But I noticed there was a fair amount of oil INSIDE the O2 sensor connector so i used electric connector cleaner and cleaned it out.

Maybe the oil leak destroyed the O2 Sensor?

I cleared the codes and we went for a drive. It drove nice and idled normal. It was driven for about 15 miles yesterday. Later that night , he tells me the check engine light came back on.

Today I go to his place and retrieve the codes.
P0150 and P0174

So I remove the right front O2 sensor from his rig (my O2 sensor.....)


(I accidentally touched the tip that is why its not ALL black)

Then I remove the #2 and # 6 spark plug respectively


#6


then I removed the #1 spark (bank 1)


I reinstall his 02 sensor and use the hawkeye scanner and get some values with the engine warm.

O2 Sensor Upstream Bank A (front left) .050v to 750v = Normal
O2 Sensor Downstream Bank A (Rear left) .034v to 567v = Normal

O2 Sensor Upstream Bank B (Front right) .113v to 128v = Not Normal
O2 sensor Downstream Bank B (Rear Right) .908 v = Not Normal

The rear right O2 Sensor was VERY BLACK too

I test the MAF readings and it was working withing similar range of mine so I am assuming it is also normal.

While I was reinstalling his original O2 sensor I noticed this carbon spray coming from the weld of the Y pipe flange

is it Cracked??

Also there is ONE vacuum leak at the manifold which I repaired a month ago but the tube has expanded... it is coming from here.

This tube circled red is what plugs into it


But the rubber gromet has expanded and it no longer fits snug. That is why you see a small piece of clear tube inside of the gromet.

Any thoughts as to what I should do?

I don't want to replace sensors and plugs to get them fouled again and be at square one.

I will be retrieving codes again tomorrow evening to get the misfire codes if they come back.

Thanks

PS...His Rover killed my O2 Sensor ...... i plugged it back in my rig and I got the P0150 code within minutes of my test drive.

 

since you have a good running parts truck try swapping in the MAF .
Fix the vacuum leak the rubber may have gotten some of the intake cleaner on it and its now lost its elasticity and has expanded you might try to put a piece of heat shrink on the end with it off the port maybe even a few layers and then fit it onto the port.
The exhaust/ header manifold is cracked

 

If the engine is sucking in to much air it will run lean, then the ECU will try and richen the fuel mixture to get it back into spec.
As we all know to much fuel and you carbon things up, like plugs and O2's.

His truck is running WAY to rich and that is why he is getting the carbon bits and the black tailpipe.
You need to fix the vacuum leak, use a small zip tie to tighten the loose hose onto the nipple, it will be a simple and easy test before you spend any real money.

 

What concerns me is the oil on the inside of the O2 sensor. Where did that come from?

 

He has some seepage from the rear valley pan gasket and the O2 harness is coated in oil from it dripping down.

I have heard of coolant and oil affecting O2 sensors this way.... but didn't think it could really happen til I disconnected the connector and saw oil inside.

 

Oh I see. I thought oil had fouled the O2 sensor, which didn't make sense because of the picture.

 

Running rich will deffinitely cause excess carbon. But the black you have on only those spark plugs tells me its oil burning and not just running rich. If it was running rich all of the spark plugs should be dark and not just a few. It could possibly be a bad vavle seal causing oil to leak into those cylinders. I would hate to think one with that few of miles would go bad, but it is possible, and would require the head to be taken off and have the vavles redone. But that is just my assumption from past experience with other brands of vehicles.

-keith

 

Well, a bad O2 sensor could tell just one bank of fuel injectors to fire more fuel than the other.

 

I have had a valve cover gasket leak run oil into the o2 sensor and ruin it before, you you would easliy be able to see that is where it is coming from though.

I also had a defective Bosch (direct fit) o2 that had to be sent back to Bosch. This one was put on after my bottom to top gasket/seal job, with new plugs, Etc. I now run Denso o2's which are more expensive but work great and have helped improve my mpg.

I would certainly fix the vacuum line first but then you might just have to get some new o2's

 

intake gasket leaking. Had to put a rookie in his place for a misdiag the other day on the same year.

what happens is the pcv separator gets completely stuffed and as the temperature lowers the ice builds up and causes the intake gasket to separate internally causing vacuum leaks inside and out. mostly to suck in oil from the galley and by that time its a new intake gasket and pcv separator. In rare instances it blows the thing up and blows the head gaskets and even the rear timing cover gasket.

Did the dealer at least tell you of the oil and any possible coolant leaks? I really get pissed when some other tech does the service and ignores the leaks for someone else to deal with.