aftermarket catalytic converters

I have a set of aftermarket cats from Summit on my Vic. They are louder than stock cats, but I haven't had any problems with them....or course I also don't have a CEL. :)

The shop checked everything emissions related on my car and didn't find any problems. Only thing they saw was that the wrong spark plugs were in the car. I'm not so sure they are "wrong" as a ton of people with my model Civic are using them but they technically aren't the ones designed for my model. Basically they are for the EX, DX, etc... and I have an Si. They are a hotter plug so could that be the cause of the failing catalytic converter? Or maybe the aftermarket cat was just a pos? I hope those hotter plugs didn't cause any engine damage. I'm sending the bad cat back today so I'll see what the manufacturer says.

Edit - Even the O2 sensors passed the wideband test. They looked fine. The parts manager who originally said they were white on the ends and that it looked like my car was running lean wasn't looking at the sensor properly. The technicians all said the O2 sensors were fine.

noisycricket wrote: O2 sensors don't measure HC, they measure O2.

Pretty much implied by the name. In the interest of brevity, I assume we all know what the O2 sensor does. Nevertheless, the fuel/air separation results in the free O2 picked up by the sensor. So it's the fuel's "fault," not the O2 because the O2 is always there in the same proportion.

We're talking about the same thing. I look at it from the fuel side because that's the variable.

Fair enough, but it's important to recognize the a misfire caused by a RICH condition will result in a "lean" reading at the O2 sensor. This can result in MORE fuel being added, not less. This is a detail often missed by tuners/diagnostics, and the opposite of what I thought you were saying. (O2 reading HC and leaning out the mixture)

njansenv wrote: Fair enough, but it's important to recognize the a misfire caused by a RICH condition will result in a "lean" reading at the O2 sensor. This can result in MORE fuel being added, not less. This is a detail often missed by tuners/diagnostics, and the opposite of what I thought you were saying. (O2 reading HC and leaning out the mixture)

We're totally in sync on that. Actually, I'm going through this problem on my beater Toyota Camry. I need a cat for the NOX but the aborted smog test showed high HC as well. So I have a lean misfire which is buggering the (new) O2 sensor reading.

I could install a cat and pass the smog test, at least this time. If I don't cure the other problem, I'll need a new cat by the next test.

Definitely do not put an AM catalyst on your 02 Cabrio. OBDII compliant or not, AM cats just aren't effecient enough to pass the cars own catalyst monitors. I have warrantied 4 AM cats on VWs last year. Some of them twice before we just bit the bullit and put on a factory catalyst. Unfortunately most modern emission systems are so stringent on thier OBDII monitors that even though the car may pass a tailpipe tests, the ECU will still fail it because it can't store enough oxygen. And yes, Honda and Toyota are known for having a slow O2 sensor trick the ECU into thinking it's a bad catalyst. It is always recommended to replace the O2 sensors when you replace the cat(s), so maybe you can try them first.

Travis_K wrote: My friend had a aba swapped mk2 gti and it constantly set cam position sensor codes. He thought it was probably a wiring problem. It could also have been related to the fact that the crank gear for the timing belt was no longer firmly attached to the crank though. lol

Sounds like it may be as simple as incorrect belt timing. That code will set if the belt is one tooth off. I've even had them set that code when the parts dept gave me the wrong belt (too long) and ended up only being a half tooth off. If that lower belt sprocket is loose, it could be the problem. But how is it loose? It's sandwiched between the crank and the pulley with a notch to keep it centered.