Failed Emissions Test
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Joined: Nov 2007
Posts: 22,415
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From: Denver Metro Area, CO
I really doubt your wiring job has anything to do with it, at least it wouldn't for the time being - not until the connections become corroded.
41 says the engine is running lean, despite what your nose is telling you. I guess it could be the computer thinks it's running lean so it's richening up the mixture and this is what your nose is telling you.
I don't know what it may use besides the O2 sensor to determine it's running lean nor how it adjusts for that, but I'd be looking in the carburetor area.
At this point - assuming the wiring is OK - I would want to assume the O2 sensor is giving the correct information to the computer.
13 has always been the IAC (aka ISC, the electric motor that controls the idle speed) or TPS (Throttle Position Sensor) in my experience.
When you start it up and have it do its test, it should initially begin at a fast idle and slowly lower down to normal; does it do this?
41 says the engine is running lean, despite what your nose is telling you. I guess it could be the computer thinks it's running lean so it's richening up the mixture and this is what your nose is telling you.
I don't know what it may use besides the O2 sensor to determine it's running lean nor how it adjusts for that, but I'd be looking in the carburetor area.
At this point - assuming the wiring is OK - I would want to assume the O2 sensor is giving the correct information to the computer.
13 has always been the IAC (aka ISC, the electric motor that controls the idle speed) or TPS (Throttle Position Sensor) in my experience.
When you start it up and have it do its test, it should initially begin at a fast idle and slowly lower down to normal; does it do this?
Senior User
Joined: Mar 2012
Posts: 153
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From: Bermuda Dunes, CA
Personally I don't care for the splice in type, the small amounts of voltage generated by the sensor quickly are interfered with, when any extra resistance comes in to play, I'd solider it up and retest it, if it smells richer, then good, richer burns cooler which will give you lower nox, but higher CO, you had lots of room on the CO, your only worry then would be at that point if your ignition system and converters would keep up with any potential HC. Solider it and retest, lets see what you get.
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Senior User
Joined: Dec 2011
Posts: 104
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From: Tustin, CA
I took the o2 sensor off and soldered the connection. It's not pretty, but it'll do. I also cleaned up the connector where the o2 sensor plugs in while I had it out. After re-installing the o2 sensor I warmed up the truck and re-ran the koeo and koer tests, both of which returned code 11. I then took it out for a couple of miles. It runs better now with all of the sensors working and it seems to have much better throttle response and a little more power now than before we started changing the sensors.
Now I just have to decide if I want to try running it through the emissions test with or without replacing the cat. On that subject, there are two catalytic converters on this truck. The first one is more expensive than the second one. I figure (just guessing) the first one does most of the work and that's probably why it costs more. Any thoughts on whether replacing the second cat would improve the emissions numbers enough to pass the test?
Now I just have to decide if I want to try running it through the emissions test with or without replacing the cat. On that subject, there are two catalytic converters on this truck. The first one is more expensive than the second one. I figure (just guessing) the first one does most of the work and that's probably why it costs more. Any thoughts on whether replacing the second cat would improve the emissions numbers enough to pass the test?
Posting Guru
Joined: Jun 2004
Posts: 1,092
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From: Casa Grande
From what I understand, you can replace both the old style cats with 1 new style free flow cat. Don't take that as gospel, check with a local exhaust shop. I know when I had the exhaust redone on the 97 I had they did that, and the 85 I have now has had it done before I got it.
Senior User
Joined: Mar 2012
Posts: 153
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From: Bermuda Dunes, CA
Peoples republic of southern california insists that if it had 2 from the factory, it always must have two, even if one new one would work and turn lead in to gold and save the world, the peoples republic says no. I'd go test it, esp if you're feeling a noticeable difference, worst that can happen is you're still not there and have to spend the big money on both cats...
Old School Hot Rodder
Joined: Feb 2006
Posts: 6,472
Likes: 11
From: Exmore, VA
Ok, one item, the ethanol enriched gas the government forces us to buy for the Iowa corn farmers gives O2 sensors a false lean condition. That may be what you are getting. As for the Peoples Rupublik of Kalifornia, I have heard they are really **** on exhaust systems. Anything you install has to be CARB approved, most places will list whether an item has the approval and the actual approval number. Good luck, it does sound like you're getting closer.
Senior User
Joined: Mar 2012
Posts: 153
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From: Bermuda Dunes, CA
The ethanol gas isn't that big of a deal. I mean in theory and on paper it seems like it would cause a considerable amount of trouble, but on my old Isuzu I have no issues, even when I had an old Mercedes with mechanical fuel injection and an o2 sensor, it ran fine and passed no problem, no lack of power and MPG seems to be the about the same.
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Posting Guru
Joined: Jun 2004
Posts: 1,092
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From: Casa Grande
Peoples republic of southern california insists that if it had 2 from the factory, it always must have two, even if one new one would work and turn lead in to gold and save the world, the peoples republic says no. I'd go test it, esp if you're feeling a noticeable difference, worst that can happen is you're still not there and have to spend the big money on both cats...
Post Fiend
Joined: Jul 2004
Posts: 8,786
Likes: 28
From: Northern California
I had to use the 2 converter route this last time.
The first converter removes most of the NOx emissions. The second one removes most of the HC and CO for what it's worth. So if your numbers are high on HC and CO but not NOx, I'd think about replacing the rear one first. If it's high in NOx and not HC or CO, then the front one first. If both then both...
If the laser thermometer states both are running too cold of exhaust through them, then I'd get both anyway. Should be about 100 degrees hotter exhaust going out than coming into the cat, for new cats. Anything below 50 degrees is iffy. If the same temps are going in and coming out, then they are toasted. This is with the system warmed up of course.
Good luck... !
Cargo Master
Joined: Dec 2004
Posts: 3,362
Likes: 22
From: Florence, SC
Originally Posted by 81-F-150-Explorer
The first converter removes most of the NOx emissions. The second one removes most of the HC and CO for what it's worth. So if your numbers are high on HC and CO but not NOx, I'd think about replacing the rear one first. If it's high in NOx and not HC or CO, then the front one first. If both then both...
In other words, are modern catalytic converters good enough that they can clean up emissions on an older vehicle that has had all of the underhood emissions removed, compared to the early 1980s factory cats with the underhood emissions equipment still in place?
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Senior User
Joined: Dec 2011
Posts: 104
Likes: 1
From: Tustin, CA
While calling around for prices for a new cat today, I found a local shop that does free diagnostics of the cat, so I'm headed there in the morning. No sense in guessing if someone who knows what's going on is willing to check it out for free.
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Senior User
Joined: Dec 2011
Posts: 104
Likes: 1
From: Tustin, CA
For the record, I'm not condoning or in anyway supporting cheating the emissions test in any way, but the answer is simple. All the nefarious tech needs is a suitable vehicle which will pass the test, then actually test the good vehicle instead of the failing vehicle.