Failed nyc emissions test

I’ve been told by my mechanic that there are only aftermarket catalytic converters available now for my well-loved car (1992 Dodge Grand Caravan w/ 150,000 miles) and that he can’t guarantee that I’ll pass inspection with an aftermarket cat.

Why wouldn’t it? An aftermarket cat must perform the same as the original cat that came on your vehicle. If it didn’t, it wouldn’t receive EPA certification to be sold as an aftermarket replacement for that vehicle application.


Catalytic converters are made to last the lifetime of a vehicle. Of course they do legitimately fail sometimes. If your catalytic converter has failed (emphasis on IF) you need to know why it failed, otherwise your new one will fail as well. Catalytic converters fail because there is a problem in the combustion process taking place in the engine, so make sure your engine is running properly. An aftermarket cat will work fine, I’d find a new shop.

I"ve seen lots of dodge/chrysler converter failures. they break apart inside and rattle. i think they have quality control issue. they can wear out even if the car is running fine. nothing wrong with aftermarket Cat.

I just want the OP to be as informed as possible.

He can’t guarantee you will pass because it may not be the source of the problem for the emission failure. Your catalytic converter may be toast but there could be an underlying factor leading to it’s failure. It could be your engine is spewing more than the converter can handle.

Thank you all for your replies. Neither my upstate or city mechanics have found anything wrong with the engine, although I don’t doubt that it may be spewing more than the cat can handle as some of you suggested. I’ve always thought I’d see 200,000 miles on this van - it otherwise basically runs like a charm. What would you guys do?

I’d look into the “Cash For Clunkers” program…

HAHA - thanks - I assume that’s a real program…I’ll check it out!

Exactly what did it fail for? By how much?

With that information I could at least render an opiinion as to whether a new converter would likely bring it into specs.

Your car is failing for one of two things: High carbon monoxide (partially burned fuel) or high hydrocarbons (unburned, raw fuel), (unless NYC tests for NOx) both of which can be corrected with fixing the root cause. Since your car is fuel injected, look for a dirty injector (multi port or throttle body), a secondary ignition (spark) issue (leakage?), vacuum leak, bad sensor, etc. You didn’t say you had a check engine light, but many times when something is out of spec, it will turn on the CEL. If so, then you can pull the code for that. Your cat will hide a problem, and clean up minor CO and hydrocarbon issues, but if the motor is running properly, you don’t really need the cat, except for the fact the law says that you do. If the cat is plugged, you’d have drivability problems, but you said it runs fine, so I’d look in a different direction.-

Benny, I agree with everything in your post except one detail: emissions specs have been set with the assumption of a cat converter in the system and I’m not sure even a good running engine with 150,000 miles could pass them without a good cat converter…perhaps not even a new engine.

I’d still like to hear what’s failing and by how much.

Let’s talk about that… Mountainbike. Maybe others can chime in. That’s an interesting comment you made about even new cars needing the cat, and I am always willing to learn all I can. I did go to school and learn about the emission systems as well as other stuff. I don’t understand why a cat is needed if the engine is burning close to 14.7:1 (stoichiometric) air/fuel ratio. That is what the computer tries to cause the engine to do. So if it is burning properly, why wouldn’t the exhaust stream be realitivily clean? And not need a cat (in theory). I’d really like to hear Testers thoughts on this…as I respect his knowledge.

I too have a very high regard for Tester’s knowledge, as I do yours, and Doc’s, OK’s, and VDC’s, and McPs, and Oldschool’s, and many other regulars. I think this has opened up an interesting subject.

While I agree that today’s systems create the overall environment that will cause as complete a combustion as possible as much as possible under the wide range of operating conditions under which an engine has to perform, while still preventing NOx emoissions as well as possible, and that even includes mutiport injection systems that spray immediately at the intake port…and now even directly into the cylinders…to maximize the surface area per volume of fuel in it’s combustion process for more complete combustion,the systems aren’t perfect, and the conditions are highly dynamic. Flame propogation isn’t perfect, the time to completely combust the fuel is limited, hit the accelerator and the injectors’ pulse widths suddenly lengthen pouring in more fuel, a bit of inert exhaust gas is needed to keep cylinder temps down (which, in addition to preventing preignition, also reduces NOx production).

I don’t have data to back this up, but I suspect that even a brand new engine would be borderline without the aid of a cat converter.

I welcome the inputs and thoughts of others on this.

Thanks - I’ll try to find out

You have been asked a number of times,“What emissions, and their values, did your Caravan fail because of?” If you don’t/won’t supply any information, no one can help you. All you have said is, “it runs like a dream”; but, failed emissions test. I wouldn’t call that, “information overload”.

Thanks everyone - I am trying to find out the info. Mechanic back tomorrow.

OK - I got the info. It failed Nox by about 6.5 (“off the scale” according to my mechanic).

Since this appears to be a Nox issue, I would suggest that you check your maintenance records to see when the spark plugs were last replaced. High Nox readings are usually traceable to bad spark plugs, or a bad EGR valve, or a worn-out catalytic converter.

Since the cat is so expensive, I would suggest first focusing on the other two possibilities that I mentioned, and maybe you will luck out in the emissions department without having to buy a new cat.

I don’t mind paying for a new cat, the problem is my mechanic said he can’t guarantee that if I do put it in that I can pass this year’s inspection.