(82,000 miles)
I've put front and rear brakes on it, transmission teardown and rebuild, rear shocks. And will need tires in the spring.


The check engine light comes on once per month.

The tech reads the system and says the catalytic converter is on its way out.


Illinois is not a smog check state.
If I do not put a new cat on it , will it harm other stuff on the motor ?

This message has been edited. Last edited by: bendable,

"Some" people would knock the guts out of the cat...

if the cat was not there or had been modified to be more free flowing, the check engine light would likely stay on.

Here behind enemy lines in Chicago we still have to go in for emission testing, my Lexus LS430 has its check engine light on now and I believe its one of the Cats. I think there is a whole liter of Cats on this car.
I don't even want to know what it will cost to change them. It might be cheaper to move.

If you run it without the cat, you may prematurely damage some other emissions hardware.. like O2 sensors. The check engine light is going to stay on. You might notice a rougher idle or decreased gas mileage. It will definitely continue to take you down the road without the cat.

Look for a “test pipe” that temporarily replaces the converter. It will tell you if it is clogged as you will have more power.

If you have upstream and downstream o2 sensors and a free flowing test pipe you might have a check engine light.

quote:

If I do not put a new cat on it , will it harm other stuff on the motor ?

I assume the trouble code is P0420 for catalytic converter efficiency, cylinder bank 1? (Although a V6 engine has two banks, the exhaust from both goes into the single cat on this car.) After over 20 years, the function of reducing emissions is probably kaput. Unless caused by breakup of the cat element, which would restrict the exhaust, the car will run just fine. Then again, a cat for that car costs roughly what your front and rear brakes did.

Is the light on constantly or intermittently? When the light is on does the car start running rough or ant change in performance?

Now a serious question, does the catalytic converter glow red? That is a sign of raw fuel being burned in the cat instead of in the engine, that’s a big problem.

GM cars of that era, if the check engine light goes out, that signifies an intermittent problem, but be aware if the car runs bad while the light is on that could indicate a more serious problem.

If it runs and drives ok I’d get a hand held scanner and clear the code every so often, that’s exactly what I do with our Jeep Liberty and it’s reoccurring P0433 code for a leak in the vapor return system. I just put a bunch of money into brakes in it and I’ve been ignoring the Check Engine light as it’s an intermittent thing and it doesn’t affect drivability, some day when it becomes a full time light on I’ll dig into it more. Until then, it’s break out the code reader and clear it as the remote starter will not work when there is a stored trouble code in the TIPM.

Had the check engine light come on because of the catalytic convertor, went to rockauto and got myself the convertor with the O2 sensors. Found a guy with a welder to do the install. I was out about 325.00 total with parts and labor.

I’ve got CEL on my 07 Wrangler. O2 sensor code. My mechanic says cats are open. So it runs just fine with the light on the dash. Doesn’t bother me.

Am going to have the light cleared off and will ask about what code it is showing

quote:

Originally posted by armored:
Here behind enemy lines in Chicago we still have to go in for emission testing, my Lexus LS430 has its check engine light on now and I believe its one of the Cats. I think there is a whole liter of Cats on this car.
I don't even want to know what it will cost to change them. It might be cheaper to move.

They don’t actually check your emissions though. They read your codes and if it has a code for emissions you will fail. If you have a way to clear the code and run up and get the test before it pops back up you will pass the emissions test. See how dumb it is. There are companies who make a device (MIL eliminator) that plugs into the bung in your exhaust between the exhaust and your o2 sensor and it makes it so you will never get that code.

Just as an example.
https://m.youtube.com/watch?v=sOV4EwF7BvU

Your catalytic converter is monitored by two O2 sensors, one upstream and one downstream.

The upstream sensor, as you would expect, measure the “contaminants” before being treated by the cat. The downstream sensor of course measures the lower level of contaminants. When the two sensors start to read values that are close the light comes on.

The easiest way to get around that is to disconnect your sensor from your exhaust downstream and tie it off under your car where it can get somewhat fresh air so that the delta reading between the two sensors is significant.

The cat can clog causing back pressure. You can either cut the cat out and replace it with a pipe or put a high flow cat in that is half the price of a normal one.

quote:

Originally posted by bendable:
Am going to have the light cleared off and will ask about what code it is showing

This is a good step, if it comes back it's probably a valid issue, some times you'll get a code that has nothing to do with an emission problem, say a gas cap is left off, loose or gone.

Knowing the code will help figure it out, if you need a new cat Rock Auto has them from $104 (closeout) to $900 and plenty inbetween.

Link

This will be the 3rd time in three months that the check engine light has come on.

quote:

Originally posted by bendable:
This will be the 3rd time in three months that the check engine light has come on.

Pretty much says there is an issue, thing with emission codes is they don't always tell you what is causing it, broken vacuum lines, gas cap, other things can cause a fault to happen when a sensor starts reading improperly.

You can go to any auto parts store, they will have a scan tool you can use for free, or they will help you to see the code(s) then post the Pxxxx code number or google it, or both

quote:

Originally posted by 1s1k:

quote:

Originally posted by armored:
Here behind enemy lines in Chicago we still have to go in for emission testing, my Lexus LS430 has its check engine light on now and I believe its one of the Cats. I think there is a whole liter of Cats on this car.
I don't even want to know what it will cost to change them. It might be cheaper to move.

They don’t actually check your emissions though. They read your codes and if it has a code for emissions you will fail. If you have a way to clear the code and run up and get the test before it pops back up you will pass the emissions test. See how dumb it is. There are companies who make a device (MIL eliminator) that plugs into the bung in your exhaust between the exhaust and your o2 sensor and it makes it so you will never get that code.

Just as an example.
https://m.youtube.com/watch?v=sOV4EwF7BvU

I have been through this before.
I went to my mechanic who cleared the code, I then went to emissions testing and they failed me because there was not enough miles put on since the code was cleared.

quote:

Originally posted by armored:

quote:

Originally posted by 1s1k:

quote:

Originally posted by armored:
Here behind enemy lines in Chicago we still have to go in for emission testing, my Lexus LS430 has its check engine light on now and I believe its one of the Cats. I think there is a whole liter of Cats on this car.
I don't even want to know what it will cost to change them. It might be cheaper to move.

They don’t actually check your emissions though. They read your codes and if it has a code for emissions you will fail. If you have a way to clear the code and run up and get the test before it pops back up you will pass the emissions test. See how dumb it is. There are companies who make a device (MIL eliminator) that plugs into the bung in your exhaust between the exhaust and your o2 sensor and it makes it so you will never get that code.

Just as an example.
https://m.youtube.com/watch?v=sOV4EwF7BvU

I have been through this before.
I went to my mechanic who cleared the code, I then went to emissions testing and they failed me because there was not enough miles put on since the code was cleared.

I’ve never heard of that in my lifetime. Why would they even care. If it passed the test it passed the test.

^^^ It didn't pass the test. The scan also checks to see if "monitors" have run. Some, for example, cat efficiency and evap system, need at least one or two "drive cycles", under very specific conditions, to reset the monitors. This is to prevent just clearing the code(s) and rushing over to the test center before the engine light comes on. They've got it covered, trust me.

I lived in Phoenix, which has emissions testing, for a time (20 years ago now). Under three years old (my vehicle was at the time), no testing required. Over that, they checked for stored trouble codes, pressure-tested the evap system, and ran the car on a dyno to check NOx. My car currently would not pass. In fact, the engine light has been on for ~7 years. The codes do not affect drivability, reliability or safety and I don't give a shit are low priority.