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Old 07-16-2012, 12:30 PM   #1
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Smog test failure

My 1998 3.4l failed the smog test today. I have the deck plate mod, which was closed for the test, and a dynomax super turbo muffler. My NO gas readings were way higher than they should be. Anyone got any ideas as to why? I'm also a California truck owner so the laws here are super strict!
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Old 07-16-2012, 06:36 PM   #2
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well when was the last time it was tuned up?
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Old 08-16-2012, 07:15 PM   #4
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Ok so i failed for the third time for high NO gasses. The truck is running perfect except for this issue. The truck is maintained and in great running condition. Its got 120k on the clock, and its the stock engine. The cat was just replaced with a magnaflow cat on monday, and it just failed again today.
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Old 08-18-2012, 06:31 AM   #5
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I found this.
http://www.nichols.nu/tip766.htm
http://www.omitec.com/en/support/tec.../gas-analyzer/
http://www.catalyticconverter.org/ne...rter-&News=216

I would think that the cel would be on if you were failing the emissions test.
now I have been dealing with emissions test since 1982, yes its a pain, but think about it this way, there is something wrong with your truck, and if its not running right you are wasting money, (gas).
my first one was a 72 mach1 and I spent the weekend before doing a complete tune up.

when was the last time you replaced the spark plugs?
did you use denso duel tip? and if so is the gap correct?
i did a triple check when I replaced mine, it was the first time I had ever messed with that type of plug.

check all the vacuum hoses under the hood. now I have never had a EGR problem, but still if it was serious i would think u would have a cel.

now when I had more money than brains I improved my 2000 mustang gt back in 2005. I either did it all or had it done, alot, but with headers I did a fresh tune and had 4 new o2 sensors, passed IL state emissions with flying colors, and they gave me a good going over... use only 87 before test.... make sure truck is very very warm, try to run her on highway before test.... hope this helps, and don't give up.
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Old 08-18-2012, 07:35 AM   #6
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^ good info above

My first thoughts were to double check condition of everything. Air filter, plugs, plug wire connections (although would have thought a cel if it was bad enough), vac hoses, clean the maf n throttle body. General stuff.

Other thought was to disconnect the battery for a while to reset everything to computer default.

Next thought was to run a bottle of cleaner through it, something like chevron fuel system cleaner, fuel system restore maybe, think there are various bottles of stuff available that supposedly specifically reduce emissions as well. Might be worth a look to clean the chambers out etc.

Let us know what you end up doing/finding
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Old 08-18-2012, 07:59 AM   #7
Have a coke and a smile and shut the f#%k up!
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Are you not getting any o2 sensor codes? I find it odd to not have any info from your computer or from the inspection machine other than incorrect exhaust readings. We have Cali emissions here in mass and our state machines will tell you why you failed and if any codes are present.
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Old 08-18-2012, 01:40 PM   #8
that was'nt a vitamin!!
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Well if you test again I'd go somewhere else and get a 2nd or 3rd opinion ya know man.
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Old 08-20-2012, 01:14 PM   #9
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Sorry for the delayed response guys, but my plan is tomorrow to change the oil, coolant, plugs, and wires. Then I'm going to take it to a different smog testing facility after i take it for a long drive to make sure everything is at operating temp for about 30 minutes. No CEL at all, and as far as I know my o2 sensors are not needing to be replaced.
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Old 08-21-2012, 11:33 AM   #10
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The following are typical for a high NOx reading. High NOx is typically a result of a lean condition.

1. Lean Fuel Mixture - Lean fuel mixtures cause high NOx. A lean fuel mixture exists when less fuel then required is delivered to the combustion chambers or when more air then necessary is added to the fuel. In either case the lack of gasoline needed to cool the combustion chambers down is not present. Combustion temperatures increase causing high nitrous oxide emissions. A lean fuel condition may be due to a vacuum leak/s and/or defective fuel control components, such as the Air Flow Meter, Engine Coolant Temperature Sensor, and O2 sensors.

2. Defective EGR System - The Exhaust Gas Recirculation system is designed to reduce NO. The EGR system consists of an EGR valve, EGR pressure sensor, vacuum hoses, and one or more vacuum switching valves or solenoids. Later model vehicles may be equipped with electronically controlled EGR valves, which do not require vacuum lines or switching solenoids. Electronic EGR systems will have these components built in.

3. Defective Catalytic Converter (CAT) Some vehicle manufactures have designed their cars to operate without EGR valves. Non-EGR equipped vehicles rely heavily on the Catalytic Converter to assist in the reduction of NO. These vehicles have tendencies to develop CAT problems sooner then those which are equipped. If you own a non-EGR equipped vehicle, and have failed the emissions test for high NOx, pay close attention to the Catalytic Converter.

4. High Engine Mileage - Over an engine's lifetime, carbon build-up develops in the engine's combustion chambers. The more miles on your engine, the more carbon build-up on the pistons, cylinder heads and valves. Carbon build-up decreases the available space for the air/fuel mixture to combust, and causes higher cylinder compression. High compression results in high temperatures and high NOx. Keep in mind this problem is usually seen in vehicles with over 150,000 miles which have been poorly maintained. The solution to this problem is called De-Carbonizing. It usually costs around two labor hours at a smog check repair station. It will remove a good amount of carbon out of an engine. This will increase combustion space, lower compression and lower NOx.

5. Low Fuel Pressure - Low fuel pressure can cause a lean fuel condition that will result in high engine combustion temperatures and high NOx reading. Low fuel pressure can be a result of a weak fuel pump, dirty/clogged fuel filter, restricted supply line, failed or weak fuel pressure regulator, or faulty return line.
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Old 08-21-2012, 12:54 PM   #11
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Oil and coolant are hardly likely to have any beneficial effect. Concentrate on things that might have something to do with your problem...

Does your CEL work at all (ie, does it come on when the key is on before you start the engine?)

Given Bamatoy's helpful insight from the trenches above, checking over the EGR as already suggested would be good, cleaning the MAF would be good, and cleaning out the carbon would be good. Fuel injector cleaner in the fuel tank might help. New fuel filter might help.

My take from a few weeks of reading various banter here is that your best bet for carbon cleaning would be to connect a small hose to the capped off port on your intake beyond the throttle body (2.7 has one, anyway - assume other engines might) and connect it to windsheild washer (disconnect the washer spray outlets and connect it), then go run the truck up over 2000 rpm and give it a shot, drive some more and give it some more - not when idling or running slowly, preferably while pulling hard up a hill. OK, I thought it was here, perhaps it was somewhere else that someone linked to from here, becasue I can't find it now.

This is assuming you are using methanol/water washer fluid. It's effectively the same thing as methanol/water injection the turbo folks use, and is evidently good at cleaning out carbon as well. Was described by someone else in one of the endless seafoam threads, and was apparently more effective at removing carbon than seafoam was.

I'll join the crowd at being surprised you don't have a check engine code/light.
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Old 08-21-2012, 01:52 PM   #12
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Yep my check engine light works, and lights up every time the key is turned on! The oil change is just because I need one, but the coolant flush I'm hoping will help lower engine temps. I'm wondering if I will foul new spark plugs if i get the de-carbonizing treatment? I don't really want to change plugs twice in one week, but I will if i must.
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Old 08-21-2012, 01:53 PM   #13
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Sorry I also forgot to mention that my truck is a non-EGR equipped model.
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Old 08-21-2012, 02:32 PM   #14
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I don't believe that the water/methanol (or just water) method of removing carbon will foul the plugs. Seafoam might or might not.

My analysis of the stuff I have read is that seafoam in the gas tank is the most likely place I'm going to put it (and have) and elsewhere is less likely, since water/meth evidently works better for cleaning carbon deposits, and seems less likely to foul the cats. While some folks are clearly amused by "huge plumes of smoke" after seafoaming in the intake, I don't get a warm fuzzy feeling about it and my expensive catalysts. Water/meth seems much less likely to cause a problem.

OTOH, if you are EGR-less, then a failed cat may be high on your list of possibles, unfortunately.
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Old 08-21-2012, 03:17 PM   #15
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Quote:
Originally Posted by Ecnerwal View Post
I don't believe that the water/methanol (or just water) method of removing carbon will foul the plugs. Seafoam might or might not.

My analysis of the stuff I have read is that seafoam in the gas tank is the most likely place I'm going to put it (and have) and elsewhere is less likely, since water/meth evidently works better for cleaning carbon deposits, and seems less likely to foul the cats. While some folks are clearly amused by "huge plumes of smoke" after seafoaming in the intake, I don't get a warm fuzzy feeling about it and my expensive catalysts. Water/meth seems much less likely to cause a problem.

OTOH, if you are EGR-less, then a failed cat may be high on your list of possibles, unfortunately.
My cat was just replaced before my third failure.
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Old 08-21-2012, 03:18 PM   #16
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Quote:
Originally Posted by BamaToy1997 View Post
The following are typical for a high NOx reading. High NOx is typically a result of a lean condition.

1. Lean Fuel Mixture - Lean fuel mixtures cause high NOx. A lean fuel mixture exists when less fuel then required is delivered to the combustion chambers or when more air then necessary is added to the fuel. In either case the lack of gasoline needed to cool the combustion chambers down is not present. Combustion temperatures increase causing high nitrous oxide emissions. A lean fuel condition may be due to a vacuum leak/s and/or defective fuel control components, such as the Air Flow Meter, Engine Coolant Temperature Sensor, and O2 sensors.

2. Defective EGR System - The Exhaust Gas Recirculation system is designed to reduce NO. The EGR system consists of an EGR valve, EGR pressure sensor, vacuum hoses, and one or more vacuum switching valves or solenoids. Later model vehicles may be equipped with electronically controlled EGR valves, which do not require vacuum lines or switching solenoids. Electronic EGR systems will have these components built in.

3. Defective Catalytic Converter (CAT) Some vehicle manufactures have designed their cars to operate without EGR valves. Non-EGR equipped vehicles rely heavily on the Catalytic Converter to assist in the reduction of NO. These vehicles have tendencies to develop CAT problems sooner then those which are equipped. If you own a non-EGR equipped vehicle, and have failed the emissions test for high NOx, pay close attention to the Catalytic Converter.

4. High Engine Mileage - Over an engine's lifetime, carbon build-up develops in the engine's combustion chambers. The more miles on your engine, the more carbon build-up on the pistons, cylinder heads and valves. Carbon build-up decreases the available space for the air/fuel mixture to combust, and causes higher cylinder compression. High compression results in high temperatures and high NOx. Keep in mind this problem is usually seen in vehicles with over 150,000 miles which have been poorly maintained. The solution to this problem is called De-Carbonizing. It usually costs around two labor hours at a smog check repair station. It will remove a good amount of carbon out of an engine. This will increase combustion space, lower compression and lower NOx.

5. Low Fuel Pressure - Low fuel pressure can cause a lean fuel condition that will result in high engine combustion temperatures and high NOx reading. Low fuel pressure can be a result of a weak fuel pump, dirty/clogged fuel filter, restricted supply line, failed or weak fuel pressure regulator, or faulty return line.
What is the procedure for de-carbonizing when it's performed at a shop? It's not like Seafoam is it?
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Old 08-21-2012, 05:40 PM   #17
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Quote:
Originally Posted by 1998tacoma4x4 View Post
My cat was just replaced before my third failure.
Well, there goes my reading comprehension score....
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Old 08-22-2012, 07:04 AM   #18
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You can easily decarbon by doing something similar to what Ecnerwal mentioned. What the ethanol/water cleaning method does is steam cleans the inside of your cylinders by injecting a SMALL...read SMALL, amount of the cleaning solution into the engine. During combustion the high heat in the cylinder with instantly steam the water, which then helps break up the carbon. It is safer than seafoam because steam will not damage or foul your plugs, or damage the catalytic converter if done properly, as a byproduct of the catalytic converter operation IS water. You just have to be careful, because this steam cleaning will clean EVERYTHING inside the cylinder. Only do it for a second, every 20-30 seconds to allow the oil and fuel lubricating properties to replenish. Otherwise you can cause ring-scoring.

Next: I would like to know, when you replaced the Cat, did you replace it with a genuine Toyota, or did you go OEM or aftermarket. You could have a brand new cat, but if the efficiency is poor, it can cause you to fail a smog test.

I am a bit confused as to your truck not having an EGR. Unless I have missed reading something in the system changes over the years, federal law requires EGR systems in all makes and models. Maybe I missed a change in the laws regarding them.

As for a CEL light being on, you can fail emissions tests without having a CEL light come on. The requirements for a closed loop system are different than for a smog test. The post cat O2 sensor does not measure things such as high NOx or SOx gasses. So the computer has no idea if the system has a minor problem resulting in a failed smog test. I have seen many cars when I was a state inspector in Texas that had no CEL, but still failed a smog test.
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Old 08-22-2012, 01:57 PM   #19
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Update, the mechanic told me that my truck model is equipped with two catalytic converters. I only replaced the rear one, assuming my truck only had one. Is it because I'm a California model? He said that this cat is a OBII safe cat. I'm kind of confused on that, because I assumed it should already be? Other than that, no other news.
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Old 08-22-2012, 01:58 PM   #20
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Quote:
Originally Posted by BamaToy1997 View Post
You can easily decarbon by doing something similar to what Ecnerwal mentioned. What the ethanol/water cleaning method does is steam cleans the inside of your cylinders by injecting a SMALL...read SMALL, amount of the cleaning solution into the engine. During combustion the high heat in the cylinder with instantly steam the water, which then helps break up the carbon. It is safer than seafoam because steam will not damage or foul your plugs, or damage the catalytic converter if done properly, as a byproduct of the catalytic converter operation IS water. You just have to be careful, because this steam cleaning will clean EVERYTHING inside the cylinder. Only do it for a second, every 20-30 seconds to allow the oil and fuel lubricating properties to replenish. Otherwise you can cause ring-scoring.

Next: I would like to know, when you replaced the Cat, did you replace it with a genuine Toyota, or did you go OEM or aftermarket. You could have a brand new cat, but if the efficiency is poor, it can cause you to fail a smog test.

I am a bit confused as to your truck not having an EGR. Unless I have missed reading something in the system changes over the years, federal law requires EGR systems in all makes and models. Maybe I missed a change in the laws regarding them.

As for a CEL light being on, you can fail emissions tests without having a CEL light come on. The requirements for a closed loop system are different than for a smog test. The post cat O2 sensor does not measure things such as high NOx or SOx gasses. So the computer has no idea if the system has a minor problem resulting in a failed smog test. I have seen many cars when I was a state inspector in Texas that had no CEL, but still failed a smog test.
The cat was a magnaflow california specific model.
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