Quick story is I have had a P0432 (Main Catalyst Efficiency Below Threshold - Bank 2) CEL since getting the car 2 months ago. Narrowed it down to the fact that the 2.8L 30v still has the original cats at 206k miles. Since it passed emmissions in Feb and I have a fresh inspection sticker, I wasn't worried about replacing the cats until I need to.

2 days ago I start up the car and notice a louder sound in the exhaust. I stick my head under the car (dressed for work) and figure a pinhole or the usual flex pipe coming off at the fitting. I didn't see anything hanging. I drive to work and notice the CEL goes out.

So the funny thing is I know exactly where to look tomorrow when I jack up the car. Somewhere before the O2 sensor on the drivers side exhaust is the leak! It was nice not seeing the orange CEL light though.

 

most likely a bad secondary 02 sensor on bank two. if you passed inspection, your cat is probably good. the fact that a hole in the exhaust made the cel go out aids in my theory. id track down another secondary 02 sensor, probably used so that way if its not the problem you didnt waste cash on a new one.

 

Could be that I suppose. Just wierd that it is the only code and the same day the leak pops up the CEL goes out. Is it possible that enough exhaust is going out the leak to be below the O2 threshold to trigger a CEL?

The previous owner had the car inspected so I don't know if he cleared the code on the way to the inspection or has a buddy that passed it or what. Who knows. I will find out soon enough.

 

like i said, try a different secodary 02 sensor and weld up exhaust. report back

 

I got under the car today. I started it up after sitting all night so I could see if some water vapors would be shooting out an opening. Sure enough drivers side connector pipe just after the O2 sensor. Exhaust blowing by on both sides of the connector. Small but noticeable.

Then while checking out the rest of the pipes, I noticed a hole on the drivers side connector pipe. Literally right in the middle of the 2 bolts on that connector. That explains the LOUDNESS.

I grabbed a tube of exhaust weld stuff and literally applied the entire tube on all the fittings of both connectors. And covered up the hole. I applied small amounts over the course of a few hours while doing yard work. Letting it sit overnight.

Need to drive the A4 tomorrow and literally hope my $7 fix gets me through one day. All mullfer shops were jammed solid today. Going in Monday to replace both connectors. I don't have a lift or cutting/torches/tools so it is going in. Im done wiggling under the car up on ramps.

 

Looks like the quick fix is working OK - so far. No return exhaust leak. However the CEL came back so either the cats are no good or O2 sensors are starting to go/gone.

Now I have the mystery fluid leak. Before I had the VCG/tensioner seals/cam caps/seals replaced, it would leak some oil on the exhaust and drip a bit onto the garage floor overnight. Literally 1-2 drops and it was nice, clear oil (recently changed). After the fix it no longer leaves anything on the ground/garage.

About 3 days ago I started to notice a new colored spot on the floor. A lot darker and looks like unchanged oil. I know it is not engine oil as it is very dark compared to the previous drip marks so I don't think it is the oil pan. Also it is noticeable underneath the car and is wind blown all underneath.

Ill grab some pics when I get home. Im initially thinking axle seal or motor mount fluid leaking. It is about 2 drops overnight. Next chance I get I will clean underneath with cleaner and try to pinpoint the source.

 

what is your new cel code? and get some pics of the leak

 

Same codes they have been from the get go. P0432 and P0422.

 

Now the latest is the CEL was on for a while with the same codes. Then yesterday I fill up and the light went out? Something is intermittently setting of the CEL.

The liquid exhaust weld is still holding strong. Now I want to see how far my $7 fix will go.

 

Finally got under the car to inspect the oil leak source. Looks like it is the o-ring between the oil cooler and the block. I noticed a drip coming down where the 2 pieces meet. Next oil change I will check the 27mm nut inside the cooler that holds it in and see if that was it. May be worth it to have a new o-ring ready to go and swap that out at the same time.