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George H.
George H., ASE Certified Technician
Category: Toyota
Satisfied Customers: 18756
Experience:  ASE Master Tech 15+ years
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I have a 1992 4 Runner and I just got a new exhaust. I have

Customer Question

I have a 1992 4 Runner and I just got a new exhaust. I have a carbon monoxide monitor and I started it in the garage just to test my new exhaust and the monitor went off the chart. Shouldn't my new exhaust systema dn the catalytic converter keep the CO levels down
Submitted: 10 months ago.
Category: Toyota
Expert:  George H. replied 10 months ago.

Hello I will help,

Is there evidence that the engine is running rich? Increased fuel consumption, black spark plugs etc.?

Was the vehicle warmed up before you started it in the garage?

What is the brand and model number of the detector?

Customer: replied 10 months ago.
I don't know if it's running rich but it just passed emmissions. The CO monitor is a TPI 707. t has been running shortly before I did this test so it was warmed up
Customer: replied 10 months ago.
I sent my phone number for a call
Expert:  George H. replied 10 months ago.

Sorry I am unable to speak on the phone.

The catalytic converter has to be hot to operate, you will still get CO out the exhaust but if you have it warm and run the engine at 2000 rpm it should not be much.

Do you know the model and brand of the detector so I can see how sensitive it is? If it is for home use it will be too sensitive to use for exhaust monitering.

Expert:  George H. replied 10 months ago.

OK, I see what detector you have. That is a good one. What readings were you seeing and were you around the vehicle or in the exhaust stream?

Customer: replied 10 months ago.
Both. I got a reading by the exhaust and in the garage a ways away. Obviously it was higher by the exhaust but it got up to 250 within a few minutes standing by the front of the car.
Customer: replied 10 months ago.
The reading in the exhaust stream was over 600. Then I shut it off and opened all the doors.
Expert:  George H. replied 10 months ago.

That is pretty high. You had the cat hot and were holding the RPMs up?

Do you have the results from the smog test?

Customer: replied 10 months ago.
No. I started the car to go somewhere then decided to do the test. Turned the car off, went into the house to get the meter, went back out to the garage and started it and did the test.
Expert:  George H. replied 10 months ago.

You have to pre heat it like they do for the emission test, A cold (below 600F) cat will not operate and the exhaust just passes through then at idle it will be higher.

Do you have a percentage reading rather than the PPM reading?

Customer: replied 10 months ago.
No. My husband uses the meter for his job. I don't really know how to do anything more than the basics!
Expert:  George H. replied 10 months ago.

Do you have the results from the smog test? It should show what they measured.

Expert:  George H. replied 10 months ago.

You might find this article interesting about how much CO a vehicle will produce

Click here for article

This one as well

Customer: replied 10 months ago.
I looked over it.
Customer: replied 10 months ago.
Should I expect that this will produce CO right after start up?
Customer: replied 10 months ago.
But not after it's running for a while?
Expert:  George H. replied 10 months ago.

Do those explain what is going on for you?

Yes, CO will be produced anytime the vehicle is running and you cannot run an engine in a closed garage even for a short time. You must start it with the door open and pull outside at once.

The amount of CO will be reduced but never to a safe to breathe level even after warming up.

The second article speaks directly to running a vehicle inside a garage.

Please let me know what further questions you have about this

Thanks

Customer: replied 10 months ago.
I'm not really going to run it in the garage. I just did that to test the CO
Expert:  George H. replied 10 months ago.

As the article states it is not possible to get a good reading in the garage, simply too much CO is produced and it will damage the sensing cell in the detector. I think what you are seeing is normal and the fact you passed the emission test bears out that the vehicle is operating properly. You did prove the point that you can't run an engine inside safely.

Let me know how I can help

Thanks

Customer: replied 10 months ago.
Thanks. I just tested it again just to see something your comments made me think of. I did it right by the tail pipe over the course of about 3 -4 minutes. Every time the readings went up into the 1.000's. I stopped the car. Waited a few minutes and did it again with the same results.
Do I have any chance of having a faulty exhaust? I just had it replaced recently.
Expert:  George H. replied 10 months ago.

As long as you passed the emission test you took it is fine. If you read through those articles it explains that those levels are normal. You have to be running the engine at very high idle for the cat to operate and reduce the CO but even then you will still see those high readings.

Let me know if that is clear

Thanks

Customer: replied 10 months ago.
Sorry, Not clear to me. What does running the car at very high idle mean?
Expert:  George H. replied 10 months ago.

2000 RPM allows enough heat from the exhaust to reach the cat and cause it to start working. You have to hold the RPMs at that level while you check but again you are not going to see safe to breathe levels out the exhaust ever. They will always be that high just not as high as they would be without the catalytic converter.

Customer: replied 10 months ago.
They had told me when I replaced the exhaust system that I was in danger of having CO enter the car but I didn't have it done at a Toyota place (dumb!) and I'm a little concerned especially since at emissions I failed until I bought a new gas cap. My husband said he didn't think the emissions people knew what they were doing. Is that possible?
Customer: replied 10 months ago.
A phone call is fine.
Customer: replied 10 months ago.
It keeps saying you aren't available for a call. Are we going to do a call?
Expert:  George H. replied 10 months ago.

As I posted above I am unable to speak on the phone.

The emissions failed for evaporative emissions then you passed after the cap was installed. That is a different system from the exhaust emissions that you are testing for CO. You might go back to the shop that installed the exhaust to have them check it for leaks if you are concerned but everything you have told me so far is normal operation and I don't see anything to be concerned about

Customer: replied 10 months ago.
Okay thanks.
Expert:  George H. replied 10 months ago.

Please let me know if you have further questions. I think you were expecting another result but you are measuring normal emissions from a '92 4runner

Expert:  George H. replied 10 months ago.

If you have no further questions please complete the rating

Thank you