I have a car with 175K miles and absolutely no sign of the catalytic converter going bad aside from the crack in the exhaust maniverter. Part of the reason why my car has done so well is because it was maintained well and had a LOT of highway miles. The car was so well maintained that the original PCV valve did not clog until I parked the car for over a year. There are lots of vehicles that are on their original catalytic converters despite having well over 400K miles on it. I replaced the catalytic converter in a Lexus LS400 with only 120K miles on it because the car was not well maintained during its life and the shop determined its efficiency had dropped to somewhere in the 70% range. That's not really an excuse IMO to replace a cat but the shop was more than willing to replace it because it's an easy job that pays well and will always help a car pass even if it shouldn't. I'm just saying that if the condition of the car you received it in suggests that it wasn't really well taken care of, then it's not unreasonable to suspect that you need to give it some TLC before you splurge on that catalytic converter. I mean you said it yourself that the car has barely passed smog in the past and that this was a long time coming..
Let me put this into extremely simple terms:
If you put a BRAND NEW catalytic converter on that car, an OBD-II Catalytic Converter (90% efficiency), and the car gets a score worse than 2 HC .02 CO and 30 NOX, YOU WASTED YOUR MONEY. That's all I'm saying.. The Catalytic converter that came with the car was designed with 80% efficiency in mind, yet if you were to pull up the smog reports on that car, I can bet you the HC readings were very close if not 0... So, even if the catalytic converter had an efficiency of only 30%, you'd still pass because the car is already emitting so few emissions when it was running like a top.
A cat that has an efficiency of 60%, while technically a bad enough cat to give a check engine code, is still good enough for controlling emissions if the car isn't emitting too many things as it is. I mean, do you even have a check engine code for the cat? I just think $200, $300, $600 spent making the car run like a top and pass emissions with a substandard catalytic converter is a better idea than just buying a catalytic converter and calling it a day since the cat provides no benefit to you aside from cleaning up tailpipe emissions.
Finally, you never told us what brand of parts you were using on your car.. If you put on anything but the OEM recommended parts (Denso, NGK, etc.) then it really isn't a surprise on why you fail smog.
IMO, if the car is getting good FE, drives well, needs a new cat to pass inspection, but will only get another 200,000 miles out of a new cat...isn't that good enough? Is it necessary to spend a lot more money having a mechanic track down whatever causes the slow premature death of the cat too?
From what I gather, Honda does not make them any longer, CA does not allow remans (as of 2009), I can't add a cat down stream (as of 2009), and no aftermarket companies build one from what I can tell.
I'm pretty sure also illegal to buy/sell/install used cats. Maybe you can apply for a variance due to the unavailability of legally acceptable parts.
I tried to buy a used cat for my old Bonneville years ago, not because of emissions concerns, but because a hole had rusted through it. The guy at the junkyard back then told me it was illegal to sell used cats. I'm sure if you went to try and buy one today you would probably encounter the same thing. You may have to take it to a muffler shop and have them custom fabricate a piece of pipe so you can use a universal cat. Still worth the repair IMHO.
It is against federal law to sell used catalytic converters for the purpose of reuse. Someone suggested trying the 49 state unit, but I don't think by law they are allowed to send a 49 state unit to a California address. Even if you could get a 49 state unit it would probably be illegal for a California based garage to put it on.
I am not perfect and hence my car is not perfectly maintained either. However, I will venture to say that is far from abused.
It only gets Mobile 1 engine oil (previously mentioned)
Engine timing is spot on (previously mentioned)
No CEL (previously mentioned)
The trans was changed to Redline synthetic
The air filter is new (Fram)
The spark plugs are new (NGK 0.044" gapping) - old plugs look healthy
The timing belt/tensioner/water pump was replaced 30K ago (all OEM)
O2 sensor is OEM
New distributor (not OEM because of more than 2x price increase)
As previously mentioned numerous items that impact smog were checked (MAP, ignition, compression (+/- 2%), EGR checked, cam timing, etc.)
I admit it could use a valve adjustment because it has been a while and the fuel filter should be replaced because of its age as well. I have a OEM fuel filter and just need to put it in. Perhaps it could use a new PCV valve.
If anyone sees a way to better maintain my car such that I can more than half my HCs, I am all ears. Believe me, if there was an easy out beyond chasing down a cat I'm interested. At this point it appears that the evidence points to the cat as there aren't many items left that could have such a negative impact on HCs.
I've only owned the car for half its life so perhaps the previous owner did not maintain it as well as we would have liked. Perhaps when the distributor failed a few months ago (first thing to ever stop the car in its tracks) there had been issues with the spark leading up to the failure. There is no telling.
I think you guys may be correct that ideally I need to find a CA cat otherwise there could be issues getting it installed.
If I can get another 200k miles out of the VX, I'd be thrilled.
If you don't have a Check Engine light, then IMO that means that catalytic converter isn't in THAT BAD of shape since that should throw a code... Just because a shop says that it probably should be replaced because the efficiency is low, doesn't really mean that it needs to be replaced. I'd just try to fix everything you can before replacing the catalytic converter and by the sounds of things, you still have some stuff to do.
Have you measured the ohms value of various ground points to the battery cable? (Including the body of the o2 sensor?) Just try to get the car in top shape before buying a cat because a new cat will mask any issues that you have. You definitely should replace the PCV valve if you haven't already.. Have you used a vacuum gauge to check the vacuum? If you can, I'd replace all the vacuum hoses with new ones since the ones you have are probably old and cracked by now, possibly causing a very modest vacuum leak. How smooth is your idle? Do you have a high accuracy tachometer besides the one that comes with the car? If your car isn't stone cold butter smooth and steady idle, then I'd say you still have work to do. I'd redo all of your electrical grounds while you're at it and make sure your wiring harness doesn't have any damage because if your harness is damaged, then your o2 sensors may not function properly and while it won't throw a code, it could cause the car to ignore the o2 sensor too often and make the car run rich...
On my civic, even though I pass smog with flying colors, I found out thanks to the scan gauge that occasionally my idle would tick up from 670 to 750rpm and increase the GPH because I have a crack in the exhaust manifold right where the o2 sensor is located. This would happen when the manifold got hot from driving the car because it would expand, causing the manifold to not as tightly hold the o2 sensor and the ohms value of the o2 sensor to the battery ground cable would increase, therefore causing the car to have to ignore the o2 sensor's output which raised the idle speed. o2 sensors generate a very small electrical signal and if there is a poor electrical ground for the o2 sensor, then that signal will have trouble getting to the computer which will then ignore the data instead of using it.
It's small, subtle things like this that can cause a car to have higher than expected smog results, yet not throw any codes. It's very possible you have a bad engine wiring harness and it's getting garbage input from the o2 sensor which won't throw a code because the ECU only throws a code when the o2 sensor data becomes stagnant or slow to update, not if the readings are charging wildly or if they're inaccurate.
After a bunch of research it became clear that I was not going to be able to get a cat from Honda and no aftermarket options were available. Being that my VX is a CA car and I am living in CA, there are only two options left.
The first is to get the smog referee to provide an exception after it has been shown that the cat can't be found and that the issue is more than likely the cat. The second is to find a junkyard CA cat which can be extremely difficult based on the low volume of CA VXs.
I choose to go down the path of trying to find a cat because I did not want to be a polluter even if I could do it legally (with smog referee approval).
After a bunch of calls to Honda oriented junk yards, I located a low mileage cat from a CA VX. It was 400 miles away in Southern California, but luckly I was headed that direction to visit family anyway. The junkyard owner explained that he is surprised if he sees one of these cats once every six months and they are sold nearly instantly. I was lucky to have called when I did. A universal cat could not be used because the cat is located on the exhaust manifold.
In the end, my HC number went down by 90%. I started at 250ppm and ended after the new used cat at 20ppm. This is passing well below the limit!
For those who have Fed cars, you can get the cats without issue. On the other hand, if you have a CA car in CA you'll be feeling the pain if your cat fails. Take good car of it by keeping up the maintenance on your car to the nth degree.
Well keep this in mind: My 1998 honda Civic LX at 10 years old had a HC rating of around 0 on 15 and 25mph when 4 years old and 46K miles and this year now at 175k miles measuring 13hc on 15mph and 7hc on 25mph. While this car likely has a catalytic converter with at least 90% efficiency (OBD-II cat) and is a California car, for the car to emit only 13hc, that means without the catalytic converter it's emitting 130hc. this is also with a cracked exhaust manifold which is one piece with the catalytic converter.
So your car emitting 250HC to me says that it's emitting far too much and that the catalytic converter you got is going to have a short life. The MAX HC for my area is 64 which means that if I were to put a catalytic converter that has only 51% efficiency (failed), the car would still pass with a score of 63.7hc since I likely emit 130hc if I didn't have a catalytic converter despite my car's age.
I was wondering how you pulled that off, as I could swear it's illegal federally and in the state of California to buy, sell, or install a used catalytic converter. However, I googled it and found out that it needs to be properly tested and certified, and then it's OK.
Very interesting. I may want to research the testing and certification required. I suspect that it's not cost-effective except in cases like this where new ones are not available.