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Failed smog...

30 June 2004
Toronto, Canada
Failed smog... (Rich Idle mixture)

So I got it smogged here in Canada and it failed. I swapped cats and it made no difference.

The test that the car fails on was the HydroCarbons at Idle and Co2 at idle. The limit is 200 ppm and the car registered 850! for HC and 1.0 for Co2 and it registered 1.61 :eek: I also smell the gas rich fumes at idle.

I brought it to Woodbine Acura and replaced the PVC valve and added the Redline Injector cleaner. I re-smogged it and Co2 passed with flying colors at 0.09 and the HC came down to 740.

We then cleaned the throttle body and I'm burning the rest of the tank of fuel before I try it again but I suspect that the HC won't be much better as I still smell the fumes.

The mechanic and service manager recommends checking the timing as they believe it may be advanced and running rich. I called Shane at Autowave since they last worked on the car and was suprised at how rich it was at idle and does not believe the timing will fix it and suggested new O2 sensors which makes a lot more sense...

I don't know how to check for hose leaks but I don't know that it would cause the computer to cause a rich idle. It does make sense that the O2 sensors are bad or covered in carbon...

I don't mind checking the timing but I don't want to pay $200 just to check it... what do you think I should do?

I'm going to burn the rest of the gas (with the Redline Fuel injector cleaner) and check to see if I can get new O2 sensors or how to clean and test them... Thanks in advance.
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Get it rich condition fixed or you can [will] clog up your cats! I wouldn't burn through the gasoline, it would seem unlikely that this is causing your problem.

I suspect faulty coolant sensor, at least put it on your list of things to check. If the engine thinks it is cold: it will run rich. Failed thermostat in open position might do it too (this will show in your coolant gauge).

If you are handy you can fake the sensor output by varying the resistance of the load across the sensor wires. The book will indicate the resistance values and you can just make something up with either real resistors or a volume control....easy stuff, just have to sit down and read a bit.

I would think that both O2 sensors to be bad is under "its possible", I suspect they would throw a code first.
Thanks a bunch. I'll definitely check this. I suspect that it's one O2 sensor as I do notice uneven smoke and exhuast that I mentioned in my "fluctuating idle post" and suspected one of my cats was bad which was not the case.

Shane says that sometimes an O2 sensor may fail but the sensor heater continues to work and does not throw any check engine codes. I have a 91 so it's OBDI

I am very suspicious that my check engine bulb is out! I'm going to check to make sure it comes on during ignition then clears.

Anything I can look for / replace that is cost efficient I will try. I'll test the coolant sensor as well as all the O2 sensors. I wonder how gunked up they are... they are the original ones and may be coated in carbon or varnish like gunk...
Tested the TW engine temp sensor the resistance is to spec.

I noticed that the left tailpipe (rear manifold) produces significantly more emissions (white smoke) than the right. Once the car warms up the right tailpipe almost stops smoking completely but the left continues to produce lost of emissions.

I confirmed the check engine light is working and am about to remove both O2 sensors to see what condition they are in. I have already swapped my cats with a known good pair and this behaviour existed even before the cat swap.

Could it be bad injectors? The injector resistors are ok. No check engine light leads me to believe that ECU sees all the sensors but there may be a sensor that is intermittently working or not working optimally. Let me konw if anyone knows what could be causing this state of rich idle which looks to be only on one side of the tailpipe...
White smoke, eh? How much white smoke? For how long?

Causes of white smoke is not good: blown head gasket, cracked head or cracked block. White is water vapor...which is a no-no after the engine is up to operating temperature.

Pull the plugs and see if one is cleaner than all the rest. I'm thinking really bad things: the plug is unable to fire because of all the moisture in the cylinder. Record what you do and which plugs go where.

There isn't much to check on the O2 sensors...if you can swap them out with known good is your cheapest option. Otherwise, just replace. At least swap your existing O2 sensors to see if problem switches banks (this would be a lucky break).
It looks like the white smoke goes away after driving a bit. Definitely a lot of water vapour while the engine was warming up today esp from the left tail but it seemed to go away. BTW, I'm in Toronto and it's about 40 degrees F outside so we do generally see more smoke.

I can't seem to easily get to the O2 sensors without some help... looks like the rear one requires the removal of the exhuast and cats... damn.
Brought it to another Acura dealer yesterday. Told the service advisor the situation and spoke to the head mechanic who works on NSXs. They were really good about it and didn't even charge me for the 1+ hour of diagnostics. They believe it is the O2 sensors and said that if I bring them the sensors, they will install them, run a pre-test on the emissions unit to ensure all is well and only charge me the $95 diagnostic fee if everything checks out and I am able to pass.

Since they have the emissions testing equipment in the shop instead of having to send the car out for testing, I think they see these numbers and are more familiar with diagnosing emissions issues. Hopefully that is the problem. I'll post the detailed info on the emissions numbers and what was done to fix it when I'm all done.
O2 sensors will clog and become slow to react and still test out fine every other way. When they become sluggish the engine has a tendeny to run rich.

The car I drag race has a real-time O2 sensor monitor that shows the output on a 7 bar LED gauge. A new O2 sensor will swing quickly from lean to rich as it helps the ecu control fuel. An old or clogged sensor will noticeably become slower to react and still not throw a code for quite some time.

Honda's main website mentions that certain gas formulas found in Canada and other places may actually contribute to this.

former Honda tech
car junkie
Taken from: http://www.ahm-ownerlink.com/Maintenance/maint_faqs.asp#gasolinesFUEL


Are some gasolines better than others? What is "Top Tier Detergent Gasoline"?

In general, Honda recommends that you buy gasoline from high-volume, major name-brand stations.

To prevent the build up of deposits inside your engine and fuel system, it is important to choose fuels that contain effective detergent additives. The detergency of some US gasolines is insufficient to provide protection from such deposits. Honda recommends the use of "Top Tier Detergent Gasolines," where available. Gasoline brands with this designation meet new, voluntary standards and have demonstrated their ability to keep engines clean through a series of demanding tests. !!!!!! Significantly, Top Tier Detergent Gasoline does not contain MMT, a metallic additive that creates deposits in your engine and exhaust system; (see the MMT explanation below)!!!!!! Fuel brands that have achieved the Top Tier Detergent Gasoline designation can be identified through their marketing campaigns, and/or by fueling station signage.

What's that sulfur smell coming from my vehicle?
All gasolines contain trace amounts of sulfur. The human sense of smell can detect sulfur odor in concentrations as low as 3 to 5 parts per million in air.

The exhaust on today's catalyst-equipped Honda vehicles will emit varying degrees of sulfur odor depending on operating temperatures and conditions. On normally operating vehicles, the odor is usually noticeable when the engine is cold, right after deceleration, or after wide-open throttle acceleration.

It may not be possible to eliminate sulfur odor completely due to the various operating conditions. If the sulfur odor is overly bothersome, please contact Honda Customer Relations or your dealer for further guidance or assistance.

Sometimes my Honda seems to idle poorly, hesitate on acceleration or experience hard starting. Why is that?

All parts of the U.S. have winter/summer blended fuel, which is needed to prevent cold or hot start problems. Winter fuels have higher volatility to compensate for cold dense air. Conversely, summer fuels have lower volatility and are less prone to "percolate."

If winter blended fuel is used in warm or hot weather, the higher temperature may cause the fuel to "percolate" within the fuel system.

Summer fuel may not vaporize adequately in cool weather.

These situations are normally localized and last only during a brief period of severe changes in climatic conditions. Normally, no vehicle repairs are needed for these situations.

Buy fuel from high-volume, major name-brand stations.

Some gas stations in our area sell oxygenated fuels or fuels that contain other additives. What's Honda's position on these fuels?

Do not use gasoline containing MMT (Methylcyclopentadienyl Manganese Tricarbonyl). MMT is a gasoline additive that is used by some refiners to boost octane. It contains the metal manganese. This additive contaminates your engine components and exhaust emission control system, and can lead to a significant increase in emissions and a loss in performance and fuel economy. Damage caused by the use of fuels containing MMT mat not be covered under warranty. Gasoline containing MMT is not common in the United States. It is prohibited in federal reformulated gasoline and in all California gasoline. However, MMT has been found in some fuels in the Southwest, mountain states, and the northwest area of New York State. MMT is more prevalent in gasoline sold in Canada, but lately many MMT-free fuels have become available. Regardless of location, the presence of MMT in the fuel will not be indicated on the pump, so it is important to ask your fueling station if their gasoline contains this additive. Alternatively, you may contact the customer service department of your preferred fuel brand with this question.

Some conventional gasolines are being blended with alcohol or an ether compound. These gasolines are collectively referred to as "oxygenated fuels." To meet clean air standards, some areas of the U.S. and Canada use these fuels to help reduce emissions. If you use an oxygenated fuel, be sure it is unleaded and meets the minimum octane rating requirement described in your Owner's Manual.

Before using an oxygenated fuel, try to confirm the fuel's contents. Some states/provinces require this information to be posted on the pump.

The following are the EPA-approved percentages of oxygenates:
ETHANOL (ethyl or grain alcohol): You may use gasoline containing up to 10% ethanol by volume.
MTBE (Methyl Tertiary Butyl Ether): You may use gasoline containing up to 15% MTBE by volume.
METHANOL (methyl or wood alcohol): Gasoline containing methanol is not common in North America. Your vehicle was not designed to use fuel that contains methanol. Methanol can damage fuel system components. This damage would not be covered under warranty.

Fuels that exceed the EPA's approved oxygenate percentages for conventional and reformulated gasolines must be clearly labeled on the pump. One example of such a fuel is "E85," which contains 85% ethanol. Do not use such fuels in your vehicle. These fuels will cause performance problems, and may damage your vehicle's engine, fuel system, and emission control system. This damage would not be covered under warranty.

If you notice any undesirable operating symptoms, try another service station or switch to another brand of gasoline.
On my early EFI cars the O2 sensors were recommend to be replaced at 75,000 miles.

Upon replacement the performance and MPG increased significantly.

O2 sensors are amazing things, quite the invention. They ARE a wear item though...


Here is an article:

Pity the oxygen sensor. Every day of its working life, it's exposed to extreme heat and harmful gases. This humble part has a direct effect on vehicle emissions, driveability and fuel economy, yet few motorists could identify one in a lineup. Even if you were able to find a motorist who knows what an oxygen sensor is, it's unlikely he'd be able to recognize the symptoms of a slow, worn-out or completely dead oxygen sensor. That's why we can't count on him to schedule an appointment because he thinks his vehicle needs oxygen sensor service.

When an O2 sensor fails or is beginning to fail, the vehicle owner may come to you stating "I think it needs a tuneup." There's a certain logic to this, since the symptoms can be very similar to what we used to see when ignition parts were defective or worn. These symptoms might include:

* Failing an emissions inspection.

* Excessive fuel consumption.

* Driveability problems, such as engine surging or hesitation.

* The Check Engine or oxygen sensor light appears (on earlier vehicles).

* The on-board computer stores a mixture-related diagnostic trouble code.

* Fouling spark plugs.

Oxygen sensors are not unlimited-life components. It's true that newer designs last longer than their predecessors, which explains why O2 sensor replacement intervals were often included in vehicle maintenance schedules. Today, most vehicle manufacturers have changed that strategy and consider oxygen sensors to be "replace when they fail" components. When (or if) an oxygen sensor fails, there could be several logical reasons why. These include:

* The unit has exceeded its design-life expectancy.

* The vehicle burns too much oil (causing sensor carbon fouling).

* An internal engine antifreeze leak has contaminated the sensor.

* Internal contamination by silicone (used in spray chemicals, gasket material, etc.).

* The sensor has become coated with other residual chemicals.

* External contamination by other automotive chemicals (undercoating solutions, etc.) applied in proximity to the O2 sensor.

* Fueling with contaminated or leaded gas, causing lead fouling.

Sensor Inspection & Testing

The oxygen sensor should be inspected during every engine performance service, or whenever its performance is suspect. A visual inspection alone can't verify the functionality of the oxygen sensor. An oscilloscope test of the sensor's ability to respond to changes in exhaust oxygen content, as well as a measurement of its response time, will provide a more definitive diagnosis.

To test an oxygen sensor's ability to respond to rich and lean conditions, follow these steps:

* Connect the oscilloscope leads to the O2 sensor circuit. For vehicles that use a three- or four-wire heated O2 sensor, you may have to bridge the connector leads and tap into the signal wire with an appropriate test probe at the connector plug.

* Warm the engine to operating temperature (oxygen sensors work properly only when they're hot-at least 350[degrees]F or 600[degrees]C). Run the engine at about 2500 rpm for two or three minutes to heat up the sensor.

* Hold engine speed at a steady, high idle between 1200 and 2000 rpm.

* Artificially drive the system rich (using propane) and lean (by opening the brake booster hose) as you observe the oscilloscope voltage reading. It should peg from .800 to .900 volt (full rich) to .100 to .200 volt (full lean).

Minimum and maximum sensor voltages are just part of the picture. How fast these transitions occur is an equally important measure of O2 sensor health. Lean-to-rich and rich-to-lean transitions should occur in 300mS or less; anything greater may indicate a worn or contaminated sensor. An oscilloscope or graphing multimeter is essential for this test.

A limited number of vehicles are equipped with a new type of oxygen sensor called an air/fuel ratio sensor. Unlike the toggling voltage produced by conventional sensors, the air/fuel ratio sensor produces a linear voltage signal. Testing methods are also different. This type of sensor allows more precise monitoring and correction of the fuel mixture than was possible with conventional O2 sensors, and may receive more widespread use in the future.

Regardless of their performance characteristics, all oxygen sensors are now heated. Heating the sensor gives it a longer design life, in part because it can be placed further downstream in the exhaust system. This protects the sensor from the thermal shocks caused by engine heating and cooling cycles. Heated sensors also reach operating temperature quickly and begin producing a sensing voltage without having to wait for the heat of the exhaust to warm them.

Heated oxygen sensors have smaller slots in the protective tube at the tip. This limits the amount of exhaust that reaches the sensing tube, and limits the contaminants that can reach the sensor and diminish its response. Consequently a heated O2 sensor may last 100,000 miles or more.

Copyright Hearst Business Publishing Jul 2003
Provided by ProQuest Information and Learning Company. All rights Reserved.
O2 sensor meter

check out:

There will be a lot of people that will tell you that using these things as a tuning tool is not a good idea. I agree. The biggest reason I still use it is just to check the health of my o2 sensor. And I like the blinky light effect :)

My GSX use to see the 1/4 mile track often and use leaded gas so it was important to note how the o2 sensor was doing afterwards. Normally, the sensor would seem to stop working correctly for a couple of days. Eventually, it would wake up again. But using leaded gas definitely decreases the lifespan of the sensor. And I could see when the sensor was starting to slow down way before a CEL was thrown.

I also have a wideband meter and separate wideband sensor in the car I use for tuning. Nice thing to have. Much more accurate than relying on the stock factory 02 sensor. Not sure what the NSX uses but starting mid 90's some civics as well as other cars boasting improved gas economy started using wideband sensors.