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Discussion Starter #1
I'm seeking help from all experts here. I failed smog recently due to high HCs at 15mph. I replaced the stock cat about 5 years ago and have since put about 60k miles with it.

When I had the after market cat replaced there was bits of honeycomb from one of the pre cats from my 1mzfe 3.0L. is missing one of these enough to cause my failure?

What are since thing I can try to pass?
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Discussion Starter #3
It is a 1999 Solara V6.

I do have both upstream (bank1 and bank 2)nO2 Sensors and a single downstream O2 sensor. My CEL just came one this morning, P0420 is the code which was the same code which caused me to change my cat 5 years ago.

I'm not sure how large of a role the pre cat plays, but are there other things i can do to reduce the HCs at the lower speeds?

Thanks!
 

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It is a 1999 Solara V6.

I do have both upstream (bank1 and bank 2)nO2 Sensors and a single downstream O2 sensor. My CEL just came one this morning, P0420 is the code which was the same code which caused me to change my cat 5 years ago.

I'm not sure how large of a role the pre cat plays, but are there other things i can do to reduce the HCs at the lower speeds?

Thanks!
Yes. Both are important. If the pre-cat o2 sensor is bad, it might not detect extra fuel. Not sure how expensive these 3 sensors are. If cheap, it is a good idea to try 3 new sensors. Otherwise, google others possibilities like exhaust leak. But getting a new cat might still be necessary. You got an aftermarket cat last time, right? It should not be a surprise that they only last 5 years.
 

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1995 Camry LE Wagon
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It is a 1999 Solara V6.

I do have both upstream (bank1 and bank 2)nO2 Sensors and a single downstream O2 sensor. My CEL just came one this morning, P0420 is the code which was the same code which caused me to change my cat 5 years ago.
It would help to have the scanner readings for upstream and downstream O2s, not just a MIL code. Do you have a scanner?
 

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Discussion Starter #6
Yes i use Torque. Would you like to see a log of the voltage measurements for all 3 O2 sensors or something else? Thanks!
 

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Upstream O2s will be hard to diagnose with log data numbers as they change so fast. Better for you to look at real time graph if that is possible with Torque to see changes in voltage. I believe the after CAT O2 should have a constant voltage. It would also help to look at LTFTs. Get your data and do a Goggle to learn what the numbers mean to see if CAT needs replacing.
 

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Discussion Starter #8
Spent some collecting some data. Attached are screenshots shots at idle and trying to simulate 15mph. The car is running rich as indicated by the negative fuel trims. Any tips what I should look at next? Will also do additional research.
Screenshot_20191213-090105.png Screenshot_20191213-085827.png Screenshot_20191213-085747.png Screenshot_20191213-085726.png
 

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The car is running rich as indicated by the negative fuel trims.
May be running rich but those low negative FTs mean the system is able to compensate. So the computer is reducing fuel from the injectors to return combustion to stoichiometric. I assume the AFR = 0 is your after CAT O2, so that seems to be OK. Did you get a graph of upstream O2 voltages? Should see between .2 to .9 volts.

The timing advance seems high (31/34)??? Don't know what it should be. Look up timing values.

Any shortage of spark energy may cause high HC emissions. If the spark occurs at the wrong time, incomplete combustion and high hydrocarbons may result. Too much spark advance could be due to an incorrect adjustment or a defect in mechanical or vacuum advance mechanisms.
 

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Discussion Starter #10
Collected more data. I believe the sample rate for Bluetooth scanner isn't fast enough to show the oscillations of the up stream sensors Screenshot_20191213-105003.png Screenshot_20191213-104903.png Screenshot_20191213-104814.png
 

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Discussion Starter #14
I noticed when going over the car the battery terminals were very loose. I tighten them down.
I also checked the spark plugs the were a little on the white side. While I was there I swapped out two of the coil packs for fun.

After doing the above the Fuel trims now stay positive at idle and 15mph.

Could the loose terminals cause weak spark and fuel spray?

Probably a reach?
 

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After doing the above the Fuel trims now stay positive at idle and 15mph.
Positive means ECU is adding fuel to compensate for O2 signal of lean burn. This +/- of the fuel trims is normal as long as it stays within about 10% of neutral (0). It's how the system was designed. The O2s take the fuel trims from lean to rich to lean etc as that makes the CAT more efficient.

Could the loose terminals cause weak spark and fuel spray?
They could cause interruptions in voltage which could cause problems. It's possible this was your problem.

How expensive is it to do another smog test?
 

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Could the loose terminals cause weak spark and fuel spray?

Probably a reach?
Poor electrical connections can cause all sorts of odd issues. BTDT. If the terminals can no longer be tightened enough to assure good contact, replacement is in order. You'll have to do it soon anyway, so doing it now will at least eliminate one variable.
 

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Discussion Starter #17
I get one free test within 30 days, which expires soon. I will ask for an extension.

I did some research and the ECU can through codes for too advance and retarded timing which I'm not getting.

Before tightening the battery terminals I cleaned as best I could by removing them and bushing. This reset the code.

I drove almost 50 miles to clear the monitors and then got P0420 CEL.

I don't think the car's value is worth the cost of the cats. I was hoping I could a budget solution.

If there is anything else I can try I'm all ears.
 

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The CATs last almost forever, at least mine is original. Maybe you're getting an errant signal from the upstream O2. You could replace them and then see.

Is there not a provision in the emissions law that you get a pass if the problem can't be fixed, or too expensive to fix?
 

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I get one free test within 30 days, which expires soon. I will ask for an extension.

I did some research and the ECU can through codes for too advance and retarded timing which I'm not getting.

Before tightening the battery terminals I cleaned as best I could by removing them and bushing. This reset the code.

I drove almost 50 miles to clear the monitors and then got P0420 CEL.

I don't think the car's value is worth the cost of the cats. I was hoping I could a budget solution.

If there is anything else I can try I'm all ears.
California has a program that helps with cost of repairs. The station you went to is test only? Or are they authorized to do repairs too? Last I heard in 2016, the state will help with up to $700? Not sure on the value.
 

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Discussion Starter #20
I do not qualify for state assistance with smog repairs unfortunately.

I was doing some research and people mentioned you can verify a cat functionality by measuring the temperatures of inlet and outlet of each cat. This will at least help me determine which cat is bad?

Upstream O2 sensors are 10 years old
Downstream O2 sensor is 2 years old
 
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