wrong cat size ?

[dgdsm]

Someone installed an incorrect catalytic converter part (Magnaflow 94004 instead of 91004) in my vehicle shortly after I acquired it. It's had high NOx emissions since, but I don't definitively know it's the cat. The 94004 is larger than the 91004 (12" instead of 9") and I've heard conflicting things about having a cat that is too large. One shop owner said it shouldn't make a difference. The manufacturer said that with a cat that is too large, it may never reach lite-off temperature. Opinions? Suggestions? I need to fix this before too long.

 

[cavillac]

I can see both but chances are it shouldnt make a *Huge* Difference as far as having acceptable emissions, I would probably suspect another problem but then again if you're trying to pass emissions law than I probably wouldnt use a Hi Flow style catalytic converter.

 

[dgdsm]

There may be an EGR system problem... but I've only seen the EGR sensor CEL code a few times, and now not in over a month. A couple of days ago I noticed this "rotten egg smell" after about 20-30 mins of city driving, which leads me to think that the cat isn't working or is deteriorating. If the cat doesn't reach lite-off temp unless you drive it for an hour on the freeway then it wouldn't have much hope of functioning in an emissions test would it? Right now it passes on CO, fails on HC, and is way off-scale on NOx. It did worse most recently at 15mph than 25mph, which also leads me to think that it's taking too long to warm up.

 

[dgdsm]

I found something interesting on this problem today. Opening up the connection to the EGR solenoid, it turns out that the terminals were severely corroded and caked up with yellow gunk. I cleaned a lot of it out with electrical contacts cleaner, but it might stand to be cleaned some more. Could this be the culprit?

 

[91dsmgsx]

^ That could very well be the problem bad electrical connections can cause many different things including the amout of emissions your car has

 

[Jay Zarcadius]

well i wouldn't think that the bigger cat would cause too much problem, IF it was working properly. it could be that the internal material inside the cat has already broken down, and is now causing more problem than its helping. what you can't tell is if this is because of the incorrect cat, or if that could've happened either way, and the wrong cat is just a coincidence. Thats just one thing that i didnt really see mentioned. the cat not being lit is kind of an assumption, but the again my theory is too. i just know how cats that are broken down on the inside tend to behave, and you'd surely get the high readings you are if that's the case. try checking that out. you could always put the correct part in and see how it works, since you know that one's good, but cats aren't cheap so thats probably not the easiest option, but thats something else for you to look into.