Sigh....

Got the car back today and about the time I got home, CEL came on. PO420, catalytic converter. Here's the problem: the cat is less than 2 months old. Rogue had to drop the transmission which means he had to drop the exhaust system, can you guys think of anything that would cause this code to come up now other than a faulty cat? Bad O2 sensor maybe?

I don't necessarily think this was directly caused by rogue, I want to make that clear. Just wondering if something could have happened that was out of Rogue's control when the parts were being taken out or put back in. Rogue has been very patient and willing to work with me, I know if he felt this was something he did, he'd fix it. I'm just trying to figure out a way to save myself a trip back up to Justin.

Thanks guys,

-Tim

easiest thing to check for starters is to make sure the rear 02 sensor is firmly plugged in. The harness is under the carpet behind the driver's side seat. Easy to get to, and with any luck, it'll be the culprit.

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Originally Posted by tailchaser

easiest thing to check for starters is to make sure the rear 02 sensor is firmly plugged in. The harness is under the carpet behind the driver's side seat. Easy to get to, and with any luck, it'll be the culprit.

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Found it, looks to be plugged in just fine. Looked under the car and things look okay to me. I am hearing a new noise from what seems like it is coming from under the hood. Not sure what it is, sort of a whirring noise. Not a tick like I would expect from an exhaust leak.

I gotta say, I love this car, but it is making me TIRED. Let me run off the list of break downs I've had in the last 6 months:

Throwout bearing failed (replaced)
Battery failed (replaced)
blowout (I know this can't be blamed on the car, but still a repair$$)
clogged EGR port (PO402) (cleaned)
blowout (again)
Fuel pump failed (replaced)
Cat failed(replaced)
Thermostat failed (replaced)
blowout (again) (replaced 4th tire too for good measure)
Alternator failed (replaced)
Alternator failed (replaced (yes, again, bad from factory))
Battery started leaking (replaced)
radiator leak (replaced)
oil leak (fixed)
Failed clutch slave cylinder (rebuilt)
A noise coming from the back end of the car that I'm waiting on to fail,
this, possible a bad cat again, or an O2 sensor.

I love driving this car, but getting in and starting it is about to start giving me panic attacks. I'm always waiting for the next thing to break. I realize all of these parts are supposed to fail at some point, and the car does have 161,000 miles on it. But this is almost literally all at once. Most of these problems came within 3 months of each other.

Okay okay done ranting. I bought a higher mileage car, and things will break. I know this, still frustrating.

Thanks, sorry to vent.

-Tim

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Originally Posted by scorn001

I gotta say, I love this car, but it is making me TIRED. Let me run off the list of break downs I've had in the last 6 months:

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Hey man... I hear you and all, but when you pick up a high-mileage car you gotta be ready for whatever it throws you. Granted, I've been lucky with my 100K+ mile '94, but I've always had older cars in the stable... and I've been through it all and then some. The way I see it is that I don't have a car payment, and that leaves me with cash to burn on mods as long as the sucker doesn't crater on me! :rolleyes: And if it does, well, eff it... I had it coming...!

It's a bet I've been willing to take for the last 15-odd years... new cars are nice and all, but they're only fun for a while! ;)

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Originally Posted by trickyrix

Hey man... I hear you and all, but when you pick up a high-mileage car you gotta be ready for whatever it throws you. Granted, I've been lucky with my 100K+ mile '94, but I've always had older cars in the stable... and I've been through it all and then some. The way I see it is that I don't have a car payment, and that leaves me with cash to burn on mods as long as the sucker doesn't crater on me! :rolleyes: And if it does, well, eff it... I had it coming...!

It's a bet I've been willing to take for the last 15-odd years... new cars are nice and all, but they're only fun for a while! ;)

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Fair enough, you are exactly right. I knew I was trading car payments for repairs. Just happening so frequently, 2 years, no problems, then all of a sudden. I probably shouldn't have ranted because I don't want the thread to get side tracked. Just blew my top a little.

-Tim

Search for that code here and at Miata.net you will find it is a very very common code for miatas. That will also give you plenty of info to read and understand what repairs you need, if any. I think there was a thread withing the month about that code here.

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Originally Posted by scorn001

Fair enough, you are exactly right. I knew I was trading car payments for repairs. Just happening so frequently, 2 years, no problems, then all of a sudden. I probably shouldn't have ranted because I don't want the thread to get side tracked. Just blew my top a little.

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Don't get me wrong, I didn't mean to trivialize your problems, but at least you haven't had a complete catastrophic breakdown (with the engine turning itself inside-out, for example) - and you're lucky for that! Plus, most of your repairs have fallen more into the long-term maintenance category, rather than the falling-to-pieces category. I always judge my old heaps on the "have I been stranded?" scale. And... so far, so good. Ironically, the only car I've had that left me stranded was my '89 Mustang (with a bad fuel pump, that magically healed itself when I went to limp the car from its resting place to my buddy's place, where we replaced the pump)... and it was only 5 years old at the time! Knock on wood, knock on wood, knock on wood...

Anyhow... from what I've read about that code, it kinda sounds like you might need to just take 'er out and "blow out the carbon" on the highway - what we call the Oklahoma Tuneup... :D

Good luck!

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Originally Posted by trickyrix

Anyhow... from what I've read about that code, it kinda sounds like you might need to just take 'er out and "blow out the carbon" on the highway - what we call the Oklahoma Tuneup... :D

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I can give that a shot, but I gotta say, I'm a 99% highway driver. I do 100 highway miles everyday, and a good portion of that is @70 MPH+ (think I-45 @ 6 AM == North Texas Autobahn baby!).

Thanks again,

-Tim

Okay, so I'm guessing its going to be an O2 sensor seeing as how the cat is practically brand new. From what I understand, the 1st O2 sensor up near the manifold is for determining fuel/air mixture, and the 2nd is actually for determining how well the cat is performing. So it make sense that the likely culprit is the 2nd O2 sensor & not the 1st O2 sensor. Is this correct?

-Tim

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Originally Posted by scorn001

Okay, so I'm guessing its going to be an O2 sensor seeing as how the cat is practically brand new. From what I understand, the 1st O2 sensor up near the manifold is for determining fuel/air mixture, and the 2nd is actually for determining how well the cat is performing. So it make sense that the likely culprit is the 2nd O2 sensor & not the 1st O2 sensor. Is this correct?

-Tim

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You're correct about the O2 sensors. If the 2nd one is faulty, then the computer would think the cat has gone bad.

+1 on the 2nd O2 sensor, but I would check the wiring harness where it goes thru the floor and connection at the sensor itself. My bet is a broken wire since the exhaust was just dropped/re-installed.

I'm currently fighting this code myself. The problem with 0420 is it's so generic, and applies to not just our cars.

Rear o2 is a good bet. Since the exhaust was just dropped, it's possible the wiring got damaged. It's also possible that it created an exhaust leak, if that's before the cat it could cause this code AND strange new noises.

Mine might be my cat (88,000 miles on the clock,) but I'm going to get the inspection place to run a sniffer today and tell me if my emissions are actually out of range or if my sensors just think they are. Maybe talk to a shop near you, they can get better data out of the ODBII than just a code sometimes.

I replaced the cat yesterday. Car smells better, and I haven't gotten the code back... yet. It's only been about 40 miles. Going to give it a few more cycles and then get it tested.

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Originally Posted by ozone42

I replaced the cat yesterday. Car smells better, and I haven't gotten the code back... yet. It's only been about 40 miles. Going to give it a few more cycles and then get it tested.

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New cat fixed my problem the first time I got it (before this one). Now though, I just can't beleive the cat is faulty again (less that 2 months old), car doesn't smell. I'm going to get an O2 sensor this weekend and plug it in. I've had the code come back on me 3 times after clearing it each day this week. I've driven it fairly hard. I don't think this one that's going away on its own.

Hope this resolves your issue, my money is that it will.

-Tim

And you were right. Passed emissions today... though I find it interesting they don't even bother doing a sniffer test... just scan the ODBII and if the car is in tune enough to pass that, they assume it's ok?

Oh well, I'm just happy I passed emissions and finally got the car transfered into my name. Now I can get to enjoying it without worrying about it.

Would running a can of Seafoam through the system help clear things out?

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Originally Posted by Magma

Would running a can of Seafoam through the system help clear things out?

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I've got a bottle of techron I'm going to run through it in my next tank. I really think something happened with the O2 sensor though. It was fine for 2 months, not a single code generated. Then the exhaust system was dropped to do some work in the bell housing, now I can't keep the code cleared for more than a day. Wasn't a gradually increasing thing the way I would expect a build up problem would occur. I think something just broke. The car's got 162,000 miles on it now, probably time for the 2nd O2 sensor to go. (I hope anyway)

I just got a ScangaugeII, and I'm waiting for my updated version to come in, at that point I should be able to get live readings out of the O2 sensors, maybe this will give me a clue.

-Tim

I would be wary of seafoam. Over on miata.net one of the guys ran some through and it ended up CAUSING this problem. I don't think it was the seafoam itself, but the effect of cleaning out a lot of carbon in the engine... which ended up on his first o2 sensor causing it to read incorrectly and slowly.

His story has a happy ending, once he figured it out, he cleaned the front o2 and everything went back to normal.

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Originally Posted by ozone42

I would be wary of seafoam. Over on miata.net one of the guys ran some through and it ended up CAUSING this problem. I don't think it was the seafoam itself, but the effect of cleaning out a lot of carbon in the engine... which ended up on his first o2 sensor causing it to read incorrectly and slowly.

His story has a happy ending, once he figured it out, he cleaned the front o2 and everything went back to normal.

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I've always had good luck with Seafoam over the years, don't think one guy slight hiccup posted on Miata.net is going to change my ways. ;)

Seafoam has always worked here too...