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Should I refrain from driving cross country with an iffy catalytic converter?

I have a 1998 Honda Civic. About 2 years ago, my mechanic informed me that some O2 sensors had gone off, and my catalytic converter would need to be replaced at some point. He advised me to wait until failure, because it wasn’t urgent. Here I am 2 years later, it hasn’t failed me yet, and I’m preparing to move from South Carolina to Colorado, a drive of about 1,600 miles. I’m ready to get a new car, but would ideally like to wait to get it in my new state of residence. I’m wondering whether it would be safe to give my 98 Civic one more road trip before I trade it in, sell it or donate it. I don’t want to replace the converter, because it’ll probably cost as much or more than the car is worth. Can anyone advise me as to what I should do? Thank you!

If the contents of the catalytic convertor are rattling or if it has become damaged from a misfire (melted) then an exhaust restriction may occur during the trip.

If the problem is a check engine light with a P0420 code then the road trip may cure the problem, the catalyst efficiency can improve with highway driving.

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1998 is early OBD II. On that car, a code for “catalyst efficiency low” simply means that the oxygen sensors are slow to respond, which is common if they have over 100k mile on them. If that was the only symptom, there may be nothing at all wrong with the catalyst.

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That’s not exactly what P0420 means . . .

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With a 1998 car the worst thing that can happen is that you are driving an old car. Keep driving it until forever happens or you get tired of the car. The best feeling is to be warranty free.

Thanks for your reply! I do not hear any rattling whatsoever, but I do believe the mechanic said something about the O2 sensors melting. The way he described it, the car might just stop running one day, and I’ll just have to get it towed, and they could replace the converter at that point. My fear is that this could happen while I’m on the middle of my road trip. The check engine light is also related, however. I’ll give them a call in the morning to see if they have a record of whether it was a P0420 code. Thank you for your advice!

Keep a charged cell phone handy. There are tow trucks everywhere. There are motels everywhere. There are repair shops everywhere. I wouldn’t worry about it.

You’d have plenty of warning before this happened. I’m wondering about your mechanic.

O2 sensors will not make it stop running.
However, lots of other things can make a 22 y.o. Civic stop running, like a broken timing belt.
Is it caught up with general maintenance?
Has it been pretty trouble free for the last couple of years?


I would think a melted/broken O2 sensor would cause a bit of an issue for the engine computer, so I would think it might decrease power some but it wouldn’t stop running completely

I wouldrive it and hope that gentle acceleration and highway driving will blow outhe catalyticonverter.

If you are about done with the car anyway then my vote is to go ahead and drive it out West. Bring along the title to the car and if it breaks down on you be ready to give up on it there if necessary. It’s pretty unlikely to happen. Long rides are not hard on cars, local stop and go is much worse.


Generally speaking, yes I’ve kept up with general maintenance. Replaced the timing belt maybe 4 years back, and got a new battery about 1 year ago. Get biannual oil changes.

The only other thing I can say is that she’s been kind of weak in terms of acceleration and uphill driving for the past few years. But other than that, she’s been very reliable.

I have indeed experienced a decrease in power. The car doesn’t accelerate that well anymore, and is pretty pathetic going uphill if I haven’t built up some speed first.

The sensors are made of steel, near as I can tell

I’m having a hard time believing that the sensors are actually melting :thinking:


Well, now I’m not so crazy about going across country in it.

Power loss may result from an obstructed exhaust, which might indicate that the catalyst has been damaged after all. The low tech way to check for an obstructed exhaust is to put your hand next to the exhaust pipe end while the car is idling. You should be able to easily feel the individual bursts of exhaust. If it is more of a smooth stream of exhaust blowing out, the exhaust is obstructed, and the most likely culprit for that is the catalyst.

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It might be a good idea to get the converter replaced. If everything else on your car is fine, just get the cat fixed (or just be a punk and delete the thing :upside_down_face:) and then go on your journey. I guess it would be better to be safe than sorry, but it is your decision.

Which is illegal, and which would likely make the car impossible to sell when the OP gets to Colorado since they follow California emission standards


of course it’s illegal, it was a joke ¯_(ツ)_/¯