fireant

I'm getting so tired of dealing with this.

My 2000 Y7 exhaust cracked open, and the f-er's at the dealership wouldnt cover it due to being over 100K miles.

I bought a $200 Y7 replacement cat-manifold and it lasted about a year before the code came on (p0420, bad cat performance). I read about the cheapo replacements failing like this, but the OE ones go for $600+!

So I converted everything over to a 2000 Y8 manifold, Magnaflow OE Y8 Cat, two new O2 sensors (soldered extensions on the rear one), and a Y8 mid-pipe with the Y7 muffler.

I thought this would be fine, but the code is back. Spark plugs are new. Car is well-maintained and automatic so it never sees any high revs.

Does the Y7 ECU just expect more from the cat? Should I try to wrap the Y8 header for more heat going into the catalyst? Any ideas on what to try?

EL Vap133

That's odd, did you clear the codes on the ECU?

fireant

Yes, twice now. I have a scangauge that does it.

The spark plugs are less than a year old. Maybe I should sea-foam it?

EL Vap133

Are the o2 sensor wires damaged at all?

fireant

I dont think so. I was very careful about the splicing job with soldering and heat shrinking.

I bought the O2 sensors about 3 months prior to changing over trying to fix the problem. So the downstream one did run with the cheapo cat for few thousand miles before I did the changeover to Y8 style.

bazoOKA_ TOoth

I get the same code. I did what youve done and I havent been able to get rid of the code. Its been 2 yrs. Now that smog is due, I can't pass it. Im completely converting back to the stock setup. I was running rich so Im also changing the fuel pump. That might be your problem. How is your fuel efficiency?

fireant

I'm averaging ~34 mpg, mostly highway with some city. I wonder if there's other things that could make it run rich, like other sensors?

Former User

Any other CEL codes in addition to P0420? An engine that misfires or runs rich will quicly kill the catalytic converter.

Otherwise, another cause for P0420 is an exhaust leak.

fireant

Nothing else at all, and it runs fine. I'll check for an exhaust leak, that's a good idea.

What do you guys think about trying sea foam? The cat is only a month old, the O2 sensors are about 4 months old.

kab00m

Have you thought about using defoulers to bring the O2 sensors back from the exhaust gases a lil bit? Popular trick in the VW world.

fireant

Yeah, I could try that first, since its pretty cheap and easy. I dont have to pass emissions locally, I'm just annoyed by the light.

B18C5-EH2

What type of converter are you running?

fireant

Magnaflow direct fit OE replacement cat. Its not a high flow. I fixed my original post for clarity.

fireant

OK, I did some research and it looks like you are not supposed to solder the wires on most O2 sensors, as they use trace amt of O2 from within the wire sheathing to sample/compare to the O2 inside the exhaust, instead of from the potentially dirty outside air like the old ones. Sounds like fiction, but if you look it up, you'll see the Bosch says specifically not to solder the wires, but to crimp them.

Also, I found that Bosch makes an O2 sensor for the Y7 called the "alternate fit" which is the same thing but with a longer wire, which is long enough to reach without mods...and it costs a few bucks less than the normal short-wired one.

I've installed it now, and I'll do some test drives for a couple of weeks and report back.

fireant

I've made 5 trips with the new one, and no lights yet. I'll post back in this thread if the code comes back, otherwise, assume it worked!

ferio252

I've had the same problem for my Y7. Comes on at 40MPH and 65mph cruising. Just kept resetting the light.

Hope you solved it.