Question about GMC S-15

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I took my truck to emissions and the carbon minoxide is at 125 and the limit is 25. What would cause such a deadly emission so high over the limit?

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A badly tuned engine.an intake or exhaust leak causing the wrong fuel delivery,a loose or worn timing belt or a plugged catalytic converter.all of these can throw off the information relayed to the onboard computer making all systems operate erratically.

Posted on Dec 05, 2011

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Excessive carbon monoxide is usually the result of very rich mixtures. Here are some causes for rich mixtures:
1. leaking fuel injector(s)
2. excessive fuel pressure at the injectors.
3. ruptured fuel pressure regulator diaphragm
4. crankcase fuel contamination (from leaking injectors)
5. plugged PCV valve or hose
6. closed loop control system incorrectly shifted rich (bad O2 sensor)
7. false input signal to ECM due to bad sensor(s).

Posted on Jan 22, 2009

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What does it mean when it says co


CO? That means Carbon Monoxide - it's a rather toxic and poisonous gas emitted from the exhaust system.

When they check emissions on cars CO is one of the gases they measure. If the level is too high .. your car fails the emissions test. I believe in the USA the emissions test is known as the 'smog test'?

If you have a problem with excess CO emissions on a car the cause is often an incorrect fuel/air mixture or a faulty sensor called the lambda/oxygen sensor in the exhaust system

May 12, 2016 | Cars & Trucks

1 Answer

How fix that problem


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Nitrous Oxide NO is created when an engine's combustion chamber temperature reaches over 2500F. 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. newer vehicles may use an electronically controlled EGR valves, which do not require vacuum lines or switching solenoids.
The EGR system's job is to re-route a small amount of exhaust gas back into the intake manifold to help reduce combustion chamber temperatures. As mentioned above NOx is created when combustion chamber temperatures reach above 2500F.
By recirculating exhaust gas back into the intake, a small amount of the air/fuel mixture is replaced with inert gas, reducing combustion temperatures.
3. Defective Catalytic Converter Some vehicles 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 will remove a good amount of carbon out of an engine. This will increase combustion space, lower compression and lower NOx.
5. Engine Overheating - Inadequate engine cooling can will high NOx. If your vehicle's cooling system is not working efficiently, high NOx will be created. Remember high NOx nitrous oxide is created when an engine's combustion chamber temperatures reach over 2500F. You will want to make sure your vehicle's cooling system is working properly, and your vehicle's temperature gauge is always indicating normal.

Carbon Monoxide is a by-product of incomplete combustion. Carbon Monoxide exceeding maximum limits, can be due to a number of emission failures ranging from inadequate air intake to defective engine computer sensors. This condition is referred to as a "Rich Fuel Conditon".
1. Dirty Air Filter - The number one overlooked emissions component, yes, "emissions" component is the engine air filter. A dirty air filter will absolutely restrict air flow, thus disturbing the proper 14.7:1 air/fuel ratio required for optimum fuel combustion.
2. Faulty Oxygen Sensor The Oxygen Sensor is responsibly for delivering information to the ECU or ECM relating to the oxygen content in the exhaust stream after it has left the combustion chambers.
The engine control computer will determine how much fuel to inject into the combustion chambers based on this data. The more oxygen in the stream, the more fuel the computer will deliver, and visa-versa. A defective O2 sensor will cause increased carbon monoxide emissions.
3. Defective Manifold Absolute Pressure - The MAP sensor determines the level of vacuum created during an engine's intake stroke, and sends this information to the ECU. During low vacuum the MAP sensor assumes the engine's throttle is in some degree open, meaning you've stepped on the pedal. It relays this information to the ECU. The ECU, in turn, sends commands to the fuel injectors, or carburetor, to increase fuel delivery.
A defective MAP sensor will not report the correct information to the ECU, thus disturbing air/fuel ratio. Usually when the ECU senses a defective MAP sensor it will learn to ignore its data, and rely on preset values, and other sensors such as the Throttle Position Sensor, and Engine Coolant Temperature Sensor; Fuel delivery will not be as accurate and high CO may result.
4.Defective Throttle Position Sensor - Obviously a very important emissions sensor; the TPS relays information regarding the position of the air intake system's throttle plate. The throttle plate, located after the engine air filter and before the intake manifold controls the amount of air entering the combustion chambers. It is usually manipulated by the gas pedal via a cable. On late model vehicles the throttle plate may be controlled electronically. A defective throttle position sensor will confuse the ECU into thinking the vehicle's operator is demanding more or less fuel, when neither is really neccessary. Most often a faulty TPS will cause high CO, as an engine's ECU always prefers to send more fuel rather then less, in an effort to avoid a lean fuel mixture and subsequently higher engine temperatures.5. Defective Engine Coolant Temperature Sensor - Low engine temperature requires more fuel. When the ECU is unable to determine what the engine's accurate temperature is, it will not adjust fuel delivery properly; resulting in high CO. As explained above, the Engine Control Computer prefers to send more fuel rather then less to avoid a lean fuel mixture.

Hydrocarbon HC. Hydrocarbons are basically raw fuel, otherwise known as Gasoline. High Hydrocarbon (HC) emissions are almost always a sign of poor fuel ignition. However, it's not always that the engine's ignition system is responsible for high Hydrocarbon emissions.1. Improper Ignition Timing - Engine ignition timing is measured in degrees before or after Top Dead Center. Example of an ignition timing failure would be in the case where an engine's ignition timing is required to be set at 10 degrees Before Top Dead Center and instead is set to 15 degrees BTDC. This fault will not only cause a smog check "functional failure", but will increase Hyrdocarbon (HC) emissions as well. California allows 3 degrees +/- off of the manufacturer's required setting. Newer vehicle's may not have a distributor, and and no timing adjustment will be needed. On these engines timing is electronically controlled by the ECU.
2. Defective Ignition Components Your vehicle's ignition system consists of the ignition coil/s, distributor, distributor cap, distributor rotor, ignition wires, and spark plugs. If any of these components are defective the engine will produce high hydrocarbons. A common reason ignition components perform poorly is due to carbon build-up. High ignition voltage traveling through the air pockets within these components form carbon. Carbon acts as an insulator between paths of electricity, decreasing the energy required at the spark plug to ignite the air/fuel in the combustion chambers properly.
3. Lean Fuel Mixture - Any condition which will cause unmetered air to enter the intake manifold, and ultimately the combustion chambers, will cause high hydrocarbons (HC). This condition is called a lean miss-fire. Such faults as vacuum leaks and gasket leaks will cause lean fuel/air mixtures. Broken, disconnected or misrouted vacuum hoses will do the same. It is also important to note that many engine components rely on engine vacuum for proper operation. If any of these components are defective, externally or internally, they may cause large vacuum leaks as well.
4. Defective Catalytic Converter - A defective catalytic converter may be responsible for high HC, CO, and NOx emissions. The Catalytic Converter, commonly referred to as the CAT is a component designed to continue the combustion process within itself and emit a more thoroughly burned and less harmful emissions containing exhaust. The most accurate way to find out if your vehicle's CAT is working efficiently is by using an exhaust gas analyzer. Unfortunately this tool is fairly expensive.
Some obvious symptoms of a bad CAT could be any of the following:
a. Major loss of power over 15-25 mph. This may be an indication that the catalytic converter is plugged up and restricting exhaust flow.
b. Strong sulfer or rotten egg smell emitting from the exhaust on an otherwise good running vehicle. This may be an indication that the Catalytic Converter isn't burning fuel completely, instead storing it, then releasing it as hydrogen sulfide.
c. Loud rattle being heard from inside the CAT. This may indicate a broken Catalytic Converter substrate. You may want to insure this sound is not due to loose exhaust components.
5. Defective Air Injection Components - Faulty smog pump and related emissions system components will cause high HC. The air injection system is designed to introduce additional oxygen, after the metering system, to the engine exhaust as it exits the exhaust manifold, or directly before it enters the Catalytic Converter; thus burning whatever remaining fuel (HC) in the exhaust completely.
6. Low Cylinder Compression - This fault is one of the less common high HC causing problems. Reasons an engine may have low or no compression in one or more of its cylinders may include things such as burned intake or exhaust valve/s, defective valve guides and/or seals, defective piston rings, and burned head gasket/s. A wet/dry cylinder compression test will diagnose this fault. More then often if such a problem exists it will be very apparent. You should notice rough idle.

Feb 19, 2015 | Cars & Trucks

2 Answers

Emission test failed HC (PPM)


i can be, only 2 things, or both.
1: engine running way too rich.
2: dead cat.
(both happens, too)
replace the cat, might be cheaper that full engine diagnosis and repair.
in a real shop we test the cat. using up and down stream tests.
with the 5 gas analyser.
but the truth is a new CAT can hide a very filthy running motor.

Mar 12, 2013 | 1995 Geo Prizm

1 Answer

1991 olds Cutlass Ciera. 3.3l, failed the NO emission test. Results: HC ppm 12 .......limit 62 CO % 0.09 ..... limit 0.35 NO ppm 948 ..... limit 700 Before testing changed plugs, wires,PCV,oil. Also had...


Since your cat was replaced you should be looking at fuel problems...even gas cap seal....check fuel pressure,fuel regulator,and evap system.>canister or purge solinoid,o2 senser...high nox is caused by the cat or fuel problems on these engines...high pressure in the combustion chamber...lean condition>air leak on hoses,or high compression caused by carbon build up ...there is no EGR on this car so don't waste time looking for it...hope this points you to your problem

Mar 14, 2010 | 1991 Oldsmobile Cutlass Ciera

3 Answers

Failed emissions test


Hi Don,

First, thank you for asking me for my input on this. It just so happens, that I used to own a Ford ranger that had the same engine as yours. It was a 1990, but there are few changes to these model years.

Anyway, there is only one reason that your HC levels would be high. Your engine has WAY too much unburned fuel in the exhaust. The same reason applies to high CO levels. Too much fuel and/or not enough air.

Below is a link that you may find very helpful. It explains exactly what we are talking about here and also lists some of the possible causes.

EMISSIONS ANALYSIS

Incidently, when I had the same emissions failure on my truck, replacing the air filter and replacing a failed MAP sensor fixed it. - I did NOT have to replace the catalytic converter. If the numbers are as high as you listed above, you will only destroy a new converter anyway because there is obviously not enough oxygen in your exhaust system for the catalyst to function properly. Those numbers are nearly DOUBLE the allowable maximum. If the engine is running correctly and the catalyst is good, your numbers will be WAY BELOW those maximum numbers.

Please understand that I am NOT telling you to replace your MAP sensor without proper diagnosis. There are many possible causes here. Please click the link above and read the article. It will help you to understand what is going on here.

Jun 03, 2009 | 1989 Ford Ranger

1 Answer

My truck failed emissions with 125 carbon minoxide. Limit is 25.


No, the emission control for Monoxide is before the muffler system, Catalytic converter is the final adjusting device.

Jan 21, 2009 | 1987 GMC S-15 Pickup

2 Answers

EMISSIONS PROBLEM


The most likely cause of this is a faulty exhuast recirculation system.It is used to cool the combustion process preventing the formation of nitrous oxide emissions. The main building block of acidic rain.Use your emission diagram and locate the EGR valve.You will need specialized equipment to check it. Other than taking it off and checking for blocked passages from carbon build up there is little you can do yourself.

Dec 31, 2008 | 1995 Ford Contour

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