The downstream O2 Sensor is located in the exhaust path behind the catalytic converter, is monitored for proper response to assure optimum catalytic converter efficiency. The exhaust is still rich so more lean, etc. This creates a vacuum leak and causes the fuel/air mixture to lean out. If a car has a check engine light on and has P0171 and P0174 codes stored, the most likely cause is a vacuum leak. Might re-tighten header bolts as well just to be safe. An exhaust leak is an exhaust leak, regardless of. Re: small exhaust leak cause lean condition? Can't remember if your running stock exhaust but sounds like you need to loosen up all of the joints on the exhaust, possibly even to the point of removing everything except the primary pipe. If there are no intake leaks, the next step is to replace the air filter and clean the air flow meter. Check the door seals and the rear doors. Yes, an exhaust leak will make the O2 sensors read a false lean condition. Exhaust leaks can cause O2 sensors to read lean. A lean condition may cause DTC P0131, DTC P0151, DTC P0171, or DTC P0174 to set. If the mixture is artificially enriched by injecting propane into the induction system, an engine running lean should speed up and the vacuum reading should rise. Routine maintenance helps prevent many smoke related issues but old seals or gaskets and certainly a big crash can cause fluid leaks. This includes not just the O2 and MAF sensors, but the manifold air pressure -- MAP -- sensor, intake air temperature sensor and even the sensor that monitors the exhaust gas recirculation system. Common causes of a lean running condition are an improperly tuned carburetor, clogged fuel line, clogged fuel filter, or a vacuum leak. That's why is important to verify the exhaust pipe condition and repair any leak including a bad exhaust manifold gasket leak. The PCM adds extra unneeded fuel. A misfiring cylinder in a four-cylinder engine is, pardon the pun, hard to miss. In order to avoid potentially severe engine damage, it is critical that the timing and fuel mixture are correct. A ratio that has too much oxygen in it is said to be lean, whereas a ratio with too much fuel is said to be rich. If any of these conditions are present you most likely will have a converter with a Broken Substrate or one unable to keep up performance. Exhaust note will be of a higher, tinier type note. code po174 - fuel system too lean cylinder bank 2. Scuffing on the exhaust side only: The bike is running too lean, whether it's caused by the wrong jetting, clogged jets, or an air leak. 3 l while driving home it started running rough and stalled out but would start back up but idles rough and when I put in gear it runs worse and stalls I found there was a f. To inspect for an exhaust leak, start with a cold engine. This is especially true for direct injection vehicles with the lean air/fuel ratios. If left unattended long enough, valves burn out due to the leak, which causes rough running engine. As a result, the o2 interprets a rich condition and the ECM consequently subtracts fuel from the mixture and lowers the BLM. If the above check out okay, the problem is a faulty heated sensor. i already replaced maf,vac lines and hoses,dpfe,intake plenum gasket,air filter,pcv valve,. The problem is with the rubber grommets in the intake manifold bolts they will crack and cause an intake leak. Depends on where the leak is. 2004 FORD F150 P0171, P0174, P0301, Misfire and Lean Condition. Here’s a list of the typical reasons for lean and rich situations. A catalytic converter should NEVER go bad unless something causes it such as a RICH or a LEAN condition. lean in banks 1&2. The lean condition can be caused by a vacuum leak, which introduces more air into the air-fuel mixture, or by a weak fuel system, which does not input enough fuel into the air-fuel mixture. Vacuum or crankcase leaks can cause a lean condition. Check for a lean fuel mixture. This in turn can result in engine overheating, piston seizure, detonation etc. If the mixture does not. When diagnosing rich or lean trouble codes, we always start by reviewing the fuel trims. Both conditions can cause a lean fuel condition and misfiring resulting in poor performance and possible excessive exhaust emissions. Vapor recovery system. There is a sensor for each cylinder in the exhaust manifolds. This will cause you to consume more gasoline than normal, resulting in an increase in your gas expenses. I believe to be a lean condition due to it only happening when the AFR went up past 20. Re: Exhaust leak - how important to fix? If that's near the O2 sensor, it would be a good idea to get it fixed because it may be effecting your mixture control. You may notice that coolant has collected on the ground under your car or that your reservoir tank is not as high as it should be. When an engine that has computer controlled spark and fuel systems has a vacuum leak, the following events occur. With help from the spark plug experts at NGK, we'll teach you how to diagnose minor tuning issues or potentially major engine problems by examining your spark plugs. However, the mixture in the motor now becomes lean and the likelihood of knock increases. i recently replaced my manifold-to-downpipe gasket. 5) and last month started hearing this clicking noise under hood when accelerating. I eliminated the pcv system from the intake manifold to remove any problems with vacuum leak through it and cleaned my maf, tps, throttle body, and checked all seen connections. Lean Carburetion: While exhaust system popping may be considered normal, it is certainly made worse by an overly lean idle circuit. Check for a lean fuel mixture. Air / Fuel Mixture. Bike only has stage one xbow exhaust on them. Its sounds like a exhaust leak of some kind and is coming from behind the intake manifold I think?. Codes P0171 & P0174 (Too lean bank 1 & Too lean bank 2) 12 Answers I have checked all vacuum lines, sprayed carb cleaner around MAP sensor, Intake manifold gaskets, between throttle body and manifold and around all vacuum points. This will cause you to consume more gasoline than normal, resulting in an increase in your gas expenses. If the mixture is too rich (too little oxygen) or too lean (too much oxygen) than the oxygen sensor sends a signal to the ECU telling it to adjusts the. Fixed carb jets can get clogged and cause this condition. A rich fuel condition causes black colored smoke to emit from the tailpipe. In addition, if the fuel level is set too high in the float chamber, a rich mixture will result. 20) Air injection systems dilute the exhaust sample with O 2. Check out the images below, courtesy of NGK Spark Plugs, and get ready to do a little light reading the next time you pull your spark plu. What can cause this? Thanks for the help guys. I triple checked before making any tuning changes. P0171 Toyota Fuel System Lean Bank 1 P0171 Lean is a very common fault code on Toyota's. 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. A leak in the exhaust system before the O2 sensor will also cause incorrect readings. The tube in your second picture is a vacuum line that operates the secondary air injection valve. A vacuum leak is still the most likely cause of a lean code. This causes an incomplete burn which causes the fumes to explode in the exhaust system along with an audible pop or bang sound. If you don't have a scan tool, you can visually inspect under the hood for leaks. 1 and getting a lean condition. So if you have those codes and a know exhaust leak, fix the exhaust leak,. This may cause your car to internally measure appropriate levels when there is a actually a problem. I'm going to respectfully disagree on the exhaust leak/crack. I'll have to check for an exhaust leak on the passenger side - my EGR bung may be leaking a bit causing that side to think it's running leaner than it really is and causing my driver's side to run a tad rich. If the mixture is artificially enriched by injecting propane into the induction system, an engine running lean should speed up and the vacuum reading should rise. The exhaust is still rich so more lean, etc. Lean Carburetion: While exhaust system popping may be considered normal, it is certainly made worse by an overly lean idle circuit. Re: Exhaust leak - how important to fix? If that's near the O2 sensor, it would be a good idea to get it fixed because it may be effecting your mixture control. Would an intake leak effect just 1 jug? No exhaust leak in smoke test. If the O2sensor continually reads high (rich), it will cause the engine computer to lean out the fuel mixture in an attempt to compensate for the rich reading. The exhaust sensor (O2 sensor) "sees" rich, so the computer leans the mix out. However this occurs only on cylinders with bridged exhaust ports. An exhaust leak can definitely cause it to run like shit but it would take a decent size leak to be that noticeable. Be sure to check pressure at all driving modes. Then i began to wonder if it was an exhaust leak or some exhaust issue because of that breathy chugging that it often sounded like. If the mixture does not. On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1. Check out the images below, courtesy of NGK Spark Plugs, and get ready to do a little light reading the next time you pull your spark plu. Air / Fuel Mixture. At some point in the piston cycle, a momentary dry spot occurs where the metal rubs together. Note: This DTC is very similar to P0174, and in fact your vehicle may show both codes at the same time. I would reset the computer to see if it was just a glitch since this is showing a lean condition on both bank 1 and 2. Your bike could be overheating due to running lean so you may consider having your carbs cleaned or rebuilt. This vacuum condition can draw raw oxygen from outside of the system and cause a false reading. On one particular occasion, I could hear the sound of a loud vacuum leak emitted from under the hood of a Ford Explorer , even before the customer informed me that her new oxygen sensors were on the front seat. The excess fuel will damage the converter overtime and cause the code. This is especially true for direct injection vehicles with the lean air/fuel ratios. A ruptured diaphragm also allows, atmospheric pressure to enter the intake manifold. They all lead to lean conditions in the mixture. Could the exhaust leaking right at the head pipe cause a lean condition?. The main reason this condition occurs is that fuel and added detergents are not hitting the back of the intake valves. In fact, these readings were taken on a Ford Escort with one plug wire grounded. Defective EGR System- The Exhaust Gas Recirculation system is designed to reduce NO. For example, a leaking exhaust valve will make a hissing noise in the exhaust pipe while a head gasket may cause bubbling in the cooling system. Water contamination will cause a lean condition. However, the catalytic converter does not get damaged fast because this kind of issues, but in the long run you can wear out the catalytic converter a lot more quickly than it should if the air-fuel mixture was right. code po174 - fuel system too lean cylinder bank 2. Usually a bad or failing exhaust manifold will produce a few symptoms that can alert the driver of a potential issue. Most techs are used to doing pressure checks, but many do not routinely check volume. Repairs for this can run from $500 to five figures (!), depending on the powertrain. PRECISE AND SAFE - Engineered 100% safe for all vehicles & GUARANTEED TO WORK! Thick Smoke output detects even the smallest leaks. 19) CO 2 is an indicator of combustion efficiency that peaks at or near the stoichiometric air-fuel ratios, and decreases with lean or rich air-fuel ratio. The most likely cause is a damaged timing chain guide or timing chain tensioner. I had a lean running condition with it once that turned out to be a leaking EGR valve. What I've seen cause vacuum leaks on these cars, in order of likelyhood: As was stated, your crankcase vent valve and all four related pipes/hoses are suspect. ^+1 should not cause lean mixture probs or misfiring. Ford Expedition lean codes could caused by a leaky PCV hose. Then i began to wonder if it was an exhaust leak or some exhaust issue because of that breathy chugging that it often sounded like. On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1. Vacuum leaks in today's computer controlled engines can cause very serious engine damage. Have a qualified technician check it out. A leak in the rubber air intake boot past the MASS Air Flow sensor could cause a lean code. It detects the amount of oxygen in the exhaust gas compared to the outside air. P013A-O2 SENSOR 1/2 SLOW RESPONSE - RICH TO LEAN. When the A/F mixture is lean, excess oxygen is in the exhaust (the fuel burned but left extra oxygen) and the catalytic converter stores that oxygen to use later. I dont know what happens when the exhaust manifold bolts loosen up. air leaks after the maf sensor or leaks in the pcv system. I would think that it would just be an exhaust leak, and not harm the engine, but not sure. Read about Oxygen Sensor. When the O2 sensor outright fails, it produces a lean (low volt, high oxygen) reading. Turned out to be the little exhaust shield right where your problem wasright at the cylinder where the header bolts on there is a seperate piece of chrome that wraps around the header and is welded on in 2 places. Functioning like a monitor, your oxygen sensor works like this: the O2 sensor tip is located inside of your exhaust pipe, the oxygen sensor detects the percentage of oxygen in the exhaust. Note: This DTC is very similar to P0174, and in fact your vehicle may show both codes at the same time. The lean condition can be caused by a vacuum leak, which introduces more air into the air-fuel mixture, or by a weak fuel system, which does not input enough fuel into the air-fuel mixture. Note: if O2 content is above 2 to 3 percent, air dilution of the exhaust gases being measured is indicated and the accuracy of the all of the gas readings may be negatively affected. A low fuel pressure will cause a deficient fuel delivery and as a consequence a possible code P0299. They can also cause a LEAN condition as the car will suck in unmetered air, which is any air entering the intake system beyond the Air Flow Meter. Pinging (spark knock or detonation) because the EGR system is not working, the exhaust port is plugged up with carbon. I would reset the computer to see if it was just a glitch since this is showing a lean condition on both bank 1 and 2. An exhaust manifold is an OEM-style part. my question is about this code p0171. PCV System: A stuck closed PCV valve causes excessive crankcase pressure, resulting in blue/gray smoke. Leaking Carburetor Intake Boot. Poor Ignition Performance. To determine if the lean condition is the result of a vacuum leak, bring the engine up to about 2,000 RPM. air is getting into the exhaust stream upstream of that O2 sensor. Noise - If you hear excessive fan noise or a roar at all engine speeds. Catalyst System Efficiency Below Threshold. In normal operation the ECM delivers less fuel and advances spark when EGR comes in. The most common cause is the crush washer seal in the exhaust port of the cylinder. I know an intake leak or vacuum leak can cause a lean condition. Generally a dirty MAF will cause lean condition, and bad O2 sensors go rich. On one particular occasion, I could hear the sound of a loud vacuum leak emitted from under the hood of a Ford Explorer , even before the customer informed me that her new oxygen sensors were on the front seat. Solution: There a few known problems concerning rattling noises that occur at certain engine conditions: 1. In this article I am going to be discussing the 1. The OBDII trouble code P0171 - System Too Lean (Bank 1) means that the engine air-fuel mixture is too lean, or there is too much air and too little fuel. The most likely cause is a damaged timing chain guide or timing chain tensioner. The misfire and no-start condition is a coil pack and/or ignition module going out, and the lean condition is an o2 sensor that's failing. What Causes My Motorcycle to Backfire Thru the Exhaust? When a motorcycle engine has an emission system malfunction, such as an exhaust leak or a moment of running rich or running lean, backfire occurs as a result. If the EGR valve is stuck open, it will essentially cause a vacuum leak, leading to inefficient combustion, rough idling, hesitation, and sometimes stalling in extreme cases. Other Wideband Sensors. Are all the hoses snug and in place?. Spark plugs that show preignition or detonation damage may indicate a need to check timing, the operation of the cooling system and conditions that cause a lean air/fuel mixture. MAIN QUESTION: Does an air leak in the exhaust valve area cause a lean running condition? lean enough to do the below Ok, I used the title as I seem to have all of those problems and have a question or two. If it comes back again, then check your o2 sensor conenctions and make sure they are clean and good. What causes a rough idle? A rough idle can be caused by many different car faults. A lean fuel mixture (too little fuel for the amount of air in the cylinder) can cause an engine to stumble or give a rough idle as well as to run too hot, overheat, and cause a lack of power as well as engine failure. The CV carb is dependent upon vacuum to function properly. Fouling of the entire set might result from an incorrect heat range spark plug or an over-rich air/fuel mixture caused by a clogged air cleaner filter element, a sticking heat riser valve, or a faulty choke. But normal at idle and high under load is the opposite of the normal symptoms of a vacuum leak. Noise can be detected when the clutch should be engaged, during initial cold startup or when the engine is hot. Do you think that a stuck runner would cause a lean condition on both banks; do they allow more or less air than can register? I wouldn't think so but maybe. Exhaust note will be of a higher, tinier type note. it was completely blown out cause 3 of the 6 bolts were loose. An exhaust leak can trigger a Check Engine Light due to the fact that depending on the location of the leak, the. Regardless, if you have an exhaust leak that you know about, it's advisable to fix it before commencing tuning. WILLIAMS October 31, 2015 at 3:58 am. Of course, if the hole was so big that there was effectively no functioning exhaust system, then you would probably feel a loss. Had the fan motor replaced and the tech had to add a pound of freon, commented could be. Detonation (spark knock) caused by excessive ignition timing, or too high of a compression ratio and/or a lean condition in the carburetor can destroy pistons, rings, and bearings in a short period of time. The PCM adds extra unneeded fuel. I know I need to fix this, but until I do, could the leak cause any additional issues like overheating/burning exhaust valves, additional oil consumption, etc?. Our Universal, Direct-fit, CARB, High Performance and Diesel converter lines cover over 100,000 applications, including OBDII coverage for all 50 states and are certified in 58 countries around the world. Do you think that a stuck runner would cause a lean condition on both banks; do they allow more or less air than can register? I wouldn't think so but maybe. We recommend Torque Pro. Turbulence can cause an uneven distribution of the fuel droplets before ignition and cause a misfire. Basically this means that an oxygen sensor in bank 1 detected a lean condition (too much oxygen in the exhaust). A leak in the exhaust system before the O2 sensor will also cause incorrect readings. Exhaust note will be of a higher, tinier type note. Inadequate volume is a common cause of lean DTCs, especially where freeze frame data points to problems at higher rpms and engine loads. If the P0171 is combined with the P0174 code, it's very likely that the problem is caused by an intake leak. From my own experience I can confirm that an exhaust leak can definitely affect the lambda reading. Generally a dirty MAF will cause lean condition, and bad O2 sensors go rich. Try a second opinion. maf sensor dirty. If you don’t have a scan tool, you can visually inspect under the hood for leaks. I have removed my cat because I couldn't afford to replace it. Vacuum leaks generally cause hesitation or inconsistent component operation (ie, idle valve). This damage looks similar to piston damage caused by running straight gas shown in the first image, but with this piston, conditions under the piston looked normal. Its got two problems. lean in banks 1&2. In this video I show where my exhaust broke and how it effects 02 sensors and how that's not good for engine performance. On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1. Answer A is correct. Faulty oxygen sensors are also fairly common in European models, due to oil fouling in the exhaust system. Lead poisoning is a serious and sometimes fatal condition. With Cis, a leak before the O2 sensor can indeed cause the car to die. It's no secret that an exhaust leak negatively impacts wideband accuracy, or that it will skew readings lean, but how big of a hole would cause a significant reading change remained untested. finally resulting in a lean exhaust signal as the computer goes nuts trying to compensate for that lean cylinder. Coupled with the high HC readings, most of us would probably have pegged this as a lean misfire condition. Have a qualified technician check it out. Do not replace O2 sensors when you have those codes. A lean condition because of a false signal from the oxygen sensor, an out-of-calibration MAP sensor, plugged injector, low fuel pressure and/or low pump volume, open IAC, or a vacuum leak will increase HC, O2 and NOx. Water in the carburetor bowl will also cause a lean fuel condition. When an exhaust leak is present, the ECU can detect a false lean signal and respond incorrectly, adding fuel in an attempt to remedy the problem, but further exacerbate it. If left unattended long enough, valves burn out due to the leak, which causes rough running engine. This is an especially big concern with the copious self-learning EFI systems flooding the aftermarket. Exhaust note will be of a higher, tinier type note. Regardless, if you have an exhaust leak that you know about, it's advisable to fix it before commencing tuning. System Too Lean at Idle (Bank 1) What does that mean? This diagnostic trouble code (DTC) is a generic powertrain code. If you only replaced the EGR Valve and did nothing else, it must have had a ruptured diaphragm that even if the valve worked correctly, the leak would add cold air into the fuel/air mixture causing a lean condition when it needed to be rich to ignite under cold engine conditions, and so prolonging the cranking time and once the enigne had. If it comes back again, then check your o2 sensor conenctions and make sure they are clean and good. 18) O 2 and CO 2 are indicators of exhaust system integrity, sample hose and probe integrity, or both. I eliminated the pcv system from the intake manifold to remove any problems with vacuum leak through it and cleaned my maf, tps, throttle body, and checked all seen connections. Without any exhaust leak or oxygen sensor problem, there is something else making the vehicle run lean. I triple checked before making any tuning changes. FOUR-CORNER SEIZURE. A severely lean main jet can cause the engine to burn a piston (hole in top). Fuel Starvation. Next we had to eliminate all the possible causes of a lean condition or excess oxygen in the exhaust. What is a "RICH OR A LEAN CONDITION"? exhaust leak. If a car has a check engine light on and has P0171 and P0174 codes stored, the most likely cause is a vacuum leak. Could I have an exhaust leak at my midpipe? Can an exhaust leak cause the computer to throw an O2 sensor code? Exhaust Leak Cause Rich or Lean Condition:. This is by far the most complex condition in terms of tracking down the culprit because there are many factors that can mimic or contribute to a lean fuel condition. Leaking EGR valves also may cause excessive HC emissions. A cylinder leak-down test (not shown) will determine the condition of the engine seal (from the valves and compression rings), but requires a special tool and access to an air compressor. Exhaust leaks -- If there is an exhaust leak, the engine may pull the outside air into the exhaust and past the sensor. As such, the sensor will interpret it as a lean condition, assuming not enough fuel was present to burn the stowaway oxygen. Harmful exhaust emissions, with the excep-tion of NO x, are at their lowest levels when. A rich fuel mixture (too much fuel for the amount of air in the cylinder) can cause an engine to load up. Check for cracked hoses a bad gasket or a faulty EGR or PCV Valve. If a valve, for whatever reason, is not allowed to close completely, a leak in both air/fuel during the compression cycle and exhaust during the combustion cycle occurs. Brake lights staying on, are one possible symptom, and possibly overheated brakes. At engine shutdown the fuel pressure should maintain operating pressure or just below that for a substantial period of time. Lean jetting is usually accompanied by a loud, ringy,. This can cause a vacuum leak and lean condition. While O2 readings alone can generally be a good indicator of lean air/fuel mixtures, it is a good idea to compare it with the other exhaust gases as well. If the mixture does not. The fuel trims show what the computer is trying to do to correct the problem. This kind of damage can be caused by over-revving the saw, running the carburetor adjustment too lean, by ignoring an air leak in the saw's engine, or a combination of factors. as a conventional oxygen sensor by air leaks between the exhaust manifold and head, and by misfires that allow unburned oxygen to pass through into the exhaust. Aftermarket exhaust manifolds look and fit just like the exhaust manifold that came on the car when it was new, with similar flow characteristics. Coupled with the high HC readings, most of us would probably have pegged this as a lean misfire condition. A leaky EGR valve can act like a vacuum leak and cause a lean misfire at idle. With the Engine Cold, visually and physically check all Vacuum Hoses. Clarifying to avoid confusion. This causes several different problems within the engine: Cylinder power imbalance ; If leak occurs on the intake side, it causes intake flow issues with other cylinders. As a result, the o2 interprets a rich condition and the ECM consequently subtracts fuel from the mixture and lowers the BLM. The P0171 is one of the more common trouble codes. Another common cause of Ford P0171 and P0174 ean codes is an engine vacuum leak. Pressure test. Fuel pressure and intake/exhaust gaskets are the first place I'd look. What Causes Backfire? When the engine on your motorcycle has an emission system malfunction, such as an exhaust leak or a moment of running rich or running lean, backfire can occur. An exhaust leak can trigger a Check Engine Light due to the fact that depending on the location of the leak, the. exhaust leak before or near the ho2s is mounted. 1997 - 2003 F150 - code p0171 exhaust leak? - I was pulling my boat yesterday and noticed my truck was shifting from 3rd to 4th gear hard. That condition could be caused by an air leak, weak fuel pressure, an exhaust leak in the manifold upstream of the HO2S, clogged fuel injectors, wear in the throttle body, or water in the fuel. The engine's intake system depends on being completely sealed and free from leaks. When the main jet is lean the engine will experience detonation or "pinging". Smoke is a good way for testing for leaks on a sealed system such as EVAP, but may not be the best way to check for leaks in the intake as the smoke will simply pass through the intake and out of the exhaust. What can cause this? Thanks for the help guys. Exhaust Leaks. Check out the images below, courtesy of NGK Spark Plugs, and get ready to do a little light reading the next time you pull your spark plu. Most gasoline passenger and light duty trucks on the road today utilize electronically controlled fuel injection. i inspected rubber intake boot(its good),replaced 2 breather hoses. Most techs are used to doing pressure checks, but many do not routinely check volume. Turned out to be the little exhaust shield right where your problem wasright at the cylinder where the header bolts on there is a seperate piece of chrome that wraps around the header and is welded on in 2 places. Exhaust leaks and fuel mileage. If you have a vacuum leak you will see your AFR go very lean. But then a vacuum condition in the exhaust is created after the exhaust valve closes. In an internal combustion engine, the expansion of the high-temperature and hhigh pressure gases produced by combustion applies direct force to some component of the engine. Causes of Anal Leakage. That's why it's important to be aware of any unusual noises as you're driving around, as this could mean your exhaust has a hole or leak you just can't see. A/F is a ratio so a lot more un-burnt gas is seen if you are pushing 50+ psi per cylinder of fuel into the engine as compared to cruising down the road. can breathing freon from a leak in indoor ac coils cause health issues? specifically respiratory? in a condo, have an outside ac unit with 'air handler' in my laundry room, with coils I assume freon runs thru from outside (they get cold). Long answer: Most people don't realize that an exhaust will blow out gasses, and suck in air at different times of the engines run cycle. Disconnect the MAF sensor. Water contamination will cause a lean condition. Check intake vacuum at idle, and inspect vacuum hose connections. If you only replaced the EGR Valve and did nothing else, it must have had a ruptured diaphragm that even if the valve worked correctly, the leak would add cold air into the fuel/air mixture causing a lean condition when it needed to be rich to ignite under cold engine conditions, and so prolonging the cranking time and once the enigne had. Never solder the HO2S wires. Troubleshooting - Bootstrapping As stated earlier, leaks in the intake and exhaust system are the primary cause of altitude related manifold pressure problems. The faulty sensor can cause a too rich or too lean condition. Slightly lean conditions are the main reason for high NOx readings; Exhaust leak prevents converter from reducing NOx efficiently; NOx is normally tested on a dyno with engine at partial load; lambda: Should always be 1 or extremely close: Lambda is a more accurate indicator than AFR because it is actual balance of air to fuel. A leak of this type would cause the engine to run rich rather than lean as the ECM/PCM compensates by modifying injector dwell. But what causes the problem in the first place? While there can be many different conditions that lead to the P2096 code, a common cause is a leak in one of the hoses that introduce the oxygen into the exhaust system. on-boost blowing air out. A/F is a ratio so a lot more un-burnt gas is seen if you are pushing 50+ psi per cylinder of fuel into the engine as compared to cruising down the road. Notice that each of these conditions have one thing in common. Check out the images below, courtesy of NGK Spark Plugs, and get ready to do a little light reading the next time you pull your spark plu. When diagnosing rich or lean trouble codes, we always start by reviewing the fuel trims. In normal operation the ECM delivers less fuel and advances spark when EGR comes in. Please note, your Deposit doesn't constitute a payment. Thanks for your question about your GSXR. Once the engine warms up, you can hear the exhaust leak ticking away. PCV System: A stuck closed PCV valve causes excessive crankcase pressure, resulting in blue/gray smoke. Causes of Excessive Exhaust Emissions: As a general rule, excessive HC, CO, and NOx levels are most often caused by the following conditions: Excessive HC results from ignition misfire or misfire due to excessively lean or rich air/fuel mixtures ; Excessive CO results from rich air/fuel mixtures. These codes are set by the car’s computer when it sees too much oxygen in the exhaust. just recently the light has came on , and is staying on. Testing the Intake Manifold Gaskets for Vacuum Leaks creating a Lean Condition. If the lean condition is true, the sensor will read rich immediately. Checking for air and vacuum leaks. If there is an exhaust leak, the engine can cause outside air to be pulled into the exhaust and past the sensor. Thermostat defective. However, the catalytic converter does not get damaged fast because this kind of issues, but in the long run you can wear out the catalytic converter a lot more quickly than it should if the air-fuel mixture was right. A vacuum leak somewhere along bank 1 could cause a lean condition on that bank without effecting bank 2. That causes the upstream O2 sensor to see a continually lean exhaust and it adds fuel to compensate. Those codes do NOT mean the O2 sensors are bad, it means a lean condition has been detected. Air leaks or vacuum leaks can cause a lean condition and are common causes of rough idle, hesitation, stalling and hard starting. The main causes for this problem are too quick warm-up, too lean carb jetting (main jet), or too hot of a spark plug range. An exhaust leak past the converter and o2 sensors is not going to have any effect on this. This is NOx or Nitrogen Oxide. Can cause vacuum leaks in numerous ways. Once the engine warms up, you can hear the exhaust leak ticking away.