Exhaust Leak Cause Lean Condition

Misfires are one of the catalytic converter's worst enemies. Apply a soapy solution to the gasket areas and the O2 boss. Oxygen Sensor O2 Sensors are used to monitor the amount of oxygen in the engine's exhaust. 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. It could be as easy as a small vacuum hose broken. Auto Service Costs Find the prices for normal auto service activities including alignment, tuneup, timing belt replacement and more. The engine's intake system depends on being completely sealed and free from leaks. You might want to look into that. Please note, your Deposit doesn't constitute a payment. I'm going to address the issue that has so far been overlooked. This may be due to a vacuum leak, but it can also be caused by a weak or inoperative accelerator pump in a carburetor, dirty injectors, or even ignition. Backfiring caused by internal carburetor problems is a result of a defective accelerator pump. The motor is a bored out 283 with corvette cams. A weak coil or excessive rotor gas inside a distributor would affect all cylinders, not just a single cylinder. Did you change anything else? intake, exhaust etc? You might need different idle or needle jets if you did. blown, it will cause these problem. It is a full length dual unit system, LTs and MangaFlow SS that exits at the stock location with turndowns by the rear valance. ) systems where air is pumped into the exhaust manifolds, the carbon vanes inside the pump will occasionally disintegrate. Unfortunately, when we have a rich or lean condition, we usually look for external engine problems first. Cutaway on right shows a detonating cylinder, where the last portion of the air/fuel mixture self-ignites and collides with the normal combustion front. A vacuum leak somewhere along bank 1 could cause a lean condition on that bank without effecting bank 2. At some point in the piston cycle, a momentary dry spot occurs where the metal rubs together. If the ECM detects an excessively lean condition, DTC P0171 or P0174 sets. The air leak piston seizure, depending on the severity of the leak, can look like a four corner type or a lean mixture type of scoring pattern. 3 Basic Causes of Stumble. The motor is a bored out 283 with corvette cams. Are all the hoses snug and in place?. Split hose could cause vacuum leak September 15, 2007 Using a smoke machine (a device that makes and blows smoke under pressure) will quickly make the fault visible. The air/fuel ratio is measured in the exhaust stream by the oxygen (O2) sensors. Exhaust manifold leaks can be dangerous as well as cause other costly problems. Basically this means that an oxygen sensor in bank 1 has detected a lean condition (too much oxygen in the exhaust). EGR valve. With the Engine Cold, visually and physically check all Vacuum Hoses. » 5 Reasons Why Your Car Backfires. Disconnect the MAF sensor. Fuel contamination; Water, even in small amounts, can be delivered to the fuel injectors. One common yet serious concern is a flue pipe that is leaking water or condensation, or even gas. Therefore, the high EGT serves to heat the pipe more and the gases themselves become a much better source of re-ignition. Check for proper air injection system operation. That said, a vacuum leak causing inconsistency in the fuel/air mix could cause car engine cylinder to misfire. 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. A misfire will cause excess oxygen in the exhaust, even though the fuel mixture is not necessarily lean. Ford Expedition lean codes could caused by a leaky PCV hose. Backfiring caused by internal carburetor problems is a result of a defective accelerator pump. on 16v misfire. Good catch. Thinking it's the manifold gaskets because it has a rough idle when first started and cold but once it warms I think the gaskets expand and seal it and then runs halfway decent. The term anal leakage would imply that the rectal contents are leaking out through the anus. P0171 Lean bank 1 Question i have a 1999 4runner 3. 2004 FORD F150 P0171, P0174, P0301, Misfire and Lean Condition. The safest place is somewhere outside of your vehicle, far away from you. Another common cause of Ford P0171 and P0174 ean codes is an engine vacuum leak. At that point, what would have been a few hundred dollars to replace a sluggish HO2S has mutated into a problem that may cost thousands. 4 4 cylinder engines in the Toyota Corolla, Camry, Rav4 and Matrix along with the V6 3. 8 m (8500 ft). When this occurs, the operator often thinks he's got carburetor problems. When there are more than 14. 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 fired up, the lean condition caused the poor idle. Either will cause the sensor to indicate a false lean condition which, in turn, will cause the computer to make the engine run rich. Other possibilities are a bad vacuum leak. In normal operation the ECM delivers less fuel and advances spark when EGR comes in. The 16v engine, is MAF based, all air leaks from the MAF to the head intake valves will cause a lean condition, if the ECU can not correct it and for sure WOT (wide open throttle) EGR MAIN leaking. If gas filter is blocked or perhaps the gas pump pressure is reasonable, there might be higher degree of oxygen in the exhaust also. Will an Exhaust leak cause a P0171 Code ?? It's been a long time since I have posted here mainly because my truck was wearing a bow tie for awhile. How to Fix Lean Exhaust Codes Step 1. Anyway I have a 2000 silverado with the 5. The CV carb is dependent upon vacuum to function properly. Excessive oxygen readings in the exhaust will set lean codes. P1171 Fuel System Lean During Acceleration refers to a problem on the front cylinder, a lean condition caused by leaks in the hose or vacuum lines. If a main vacuum hose such as the power brake booster feed line has broken or failing off it will cause a lean backfire due to the additional air allowed into the engine intake manifold. Vacuum Leaks– With the Cadillac Escalade, the most common cause for the P0174 or P0171 code to show is a vacuum leak. Now I feel like the bike is running a little hotter and it doesn’t like to sit at a stop light as much, couple instances of ping when hot. If there is an exhaust leak, the engine can cause outside air to be pulled into the exhaust and past the sensor. Misfires & Backfires. The HO2S generates a voltage between 0. Has a 52 pilot jet in it which is very large so why it is running lean I don't understand. Therefore, Too lean and the converter is unable to convert the hydrocarbons into safe elements and may not pass a state inspection. You need to make sure no vacuum leaks are present, and this test can also be done with propane, shooting it around the intake manifold, hoses, PVC, etc and if O2 values spike, you found your leak. This is a result of working equipment, and is unlikely to cause damage. I have removed my cat because I couldn't afford to replace it. That causes the upstream O2 sensor to see a continually lean exhaust and it adds fuel to compensate. Spark plug insulator is almost white and the elctrode is without any carbon residues>>very lean condition. may happen as the exhaust valve opens. You will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a. Do not replace O2 sensors when you have those codes. Typical to an intake manifold gasket that is leaking, is an engine misfire, especially with the engine cold. Here I try to create a new diagnostic procedure to differentially diagnose an exhaust leak as the cause of a lean condition as opposed to other possible causes of lean condition that may cause. If both banks read lean, suspect air flow sensor readings, inadequate fuel delivery, fuel quality, or a jumped timing belt. I sprayed it out with carb cleaner, but did not actually test operation. If it fails, I might try one of the "messier" methods. The P0171 and P0174 code set criteria is that the long term fuel trim cell must be above 23% for 6 seconds. How much mileage, what's the condition of the catalytic converter, not often you see that code on that vehicle, Can be an intake leak, or cracked header flange causing an exhaust leak (very common). If gas filter is blocked or perhaps the gas pump pressure is reasonable, there might be higher degree of oxygen in the exhaust also. 2004 FORD F150 P0171, P0174, P0301, Misfire and Lean Condition. And always check for after- market modifications. Oil leaking out exhaust port! Help! Seriously, it is the oil that you mixed with the gas. 9 V in proportion to the increased difference. It may be partially plugged. Too rich and the catalyst can melt down. and code still popped up running lean after a few miles. So, any defect in them will cause the car to run rich or lean. I have had plenty of drama with this kx100 eating top ends and discussed it here previousl. On modern computer controlled engines this will cause the computer to turn on an amber check engine light which will give a trouble code of "system too rich" or "system too lean" Either condition will result in poor fuel mileage or possible engine damage. 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. This could be caused by a number of reasons, such as low fuel pressure, plugged fuel filter, worn fuel pump, vacuum leaks, exhaust leaks, etc. If sufficient fuel flow returns, the piston will work as normal, but the damage remains. The Pressure Test. Other things that can cause it are exhaust leaks - not really a lean condition, just a false reading - whoops saw you fixed that Check for air leaks in any intake piping between the MAF and TB. Otherwise you will need to use a air/fuel ratio measuring device like a pyrometer in the exhaust. If you want to fix this white smoke problem, the easy solution is to take your vehicle to the nearest auto body shop as soon as you notice it. I have codes being thrown which are P0171 System Too Lean - Bank No. EGR valve. When Monitored: With the engine running in closed loop mode, the ambient/battery temperature above -6. If the code returns, continue with your diagnosis. Eventually, the pistons in lean-running engines will develop enough damage to fail. The decal popping is cause by having modified the exhaust system and the tune is ever so slightly lean on the deacceleration phase. However, a vacuum leak such as rotted or loose vac hoses can also cause issues, but you usually get a check engine and the dreaded high idels response. As oxygen content increases, it causes partially burn or unburned fuel entering the system to ignite loudly. Well the rear most bolt is somehow broken off flush with the head and the shop wants to remove the enitre head to get this out, which will cost me roughly $900. A lean condition will cause it and will also damage the catalytic converter. I've also had an exhaust smell in the cabin, on colder days I would just switch on recirculate and the windows would be closed, didn't really seem to get in the car that way. The lean mixture produces more oxygen in the exhaust and the voltage drops, which causes the computer to command a rich fuel mixture. Lean conditions usually show themselves as roughness. Apply a soapy solution to the gasket areas and the O2 boss. 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 fired up, the lean condition caused the poor idle. Please note, your Deposit doesn't constitute a payment. You will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a. You also may have worn down a part of the car interior which is letting the exhaust in. 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. Let’s talk about the different colors of exhaust smoke, their causes and solutions. Other things that can cause it are exhaust leaks - not really a lean condition, just a false reading - whoops saw you fixed that Check for air leaks in any intake piping between the MAF and TB. If the lean condition is true, the sensor will read rich immediately. Low fuel pressure would affect all cylinders rather than an individual cylinder, as would most air leaks. When there are more than 14. Next we had to eliminate all the possible causes of a lean condition or excess oxygen in the exhaust. A diluted cylinder charge helps in engine fuel efficiency but at the same time presents significant challenges to combustion stability. The sound is especially loud during a cold start or when you accelerate the vehicle. Sometimes a service technician will reset the PCM and take it for a test drive. It runs very lean when doing the spark plug test. On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1. P0174 SATURN Tech Notes If the P0171 is combined with the P0174 code, it's very likely that the problem is caused by an intake leak. The fuel trims show what the computer is trying to do to correct the problem. Check for proper air injection system operation. and P0172 System Too Rich - Bank No. ) fuel pressure - system will go lean, if pressure is too low. 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. A technician is working on a vehicle equipped with a port-injected engine. The fuel is very precisely added to the incoming air. The cat will eventually break apart internally clogging the exhaust system. If it's after the turbo, it won't affect anything. 3 The driver side exhaust manifold gasket is leaking. Do not replace O2 sensors when you have those codes. Let’s talk about the different colors of exhaust smoke, their causes and solutions. Not sure if a leak in that location can cause my trims to be like that. I have codes being thrown which are P0171 System Too Lean - Bank No. Please note, your Deposit doesn't constitute a payment. For the same reason as acceleration problems, a more severe vacuum leak may make it more difficult to start your vehicle. I took the exhaust off of it to clean some things and noticed it doesn't have an exhaust gasket. Get a new exhaust collar the rubber tends to go bad after awhile and can cause leaks. Will pre-cat exhaust leak cause rich condition? I was reinstalling my exhaust, and one of the bolts broke that connects the exhaust manifold to the pipe at the flange. I found a small exhaust leak at the header collector/Y-pipe joint, shown in picture below. If one of the intake pipe came off or is loose that can cause a real bad idle. Sorry if I wasn't clear. 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. Take a look around and see if you can find the vacuum leak. Because the air flow meter is reading one value, and the vacuum leak will cause the air/fuel mixture to get leaner, you do often get trouble codes about a lean mixture or misfire trouble codes. 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. Honda CR 250 2007 lean condition problem Hi dudes! I have pretty big issue with my CR. exhaust side. Vacuum or crankcase leaks can cause a lean condition or a possibly a high idle. I am just asking if there's any way that an exhaust leak would cause a lean condition. Do not replace O2 sensors when you have those codes. The internal cylinder condition is just as important, […]. Not sure if a leak in that location can cause my trims to be like that. An engine backfire is an explosion produced by an internal. An exhaust leak past the converter and o2 sensors is not going to have any effect on this. Vacuum Leaks- With the Cadillac Escalade, the most common cause for the P0174 or P0171 code to show is a vacuum leak. 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. Air leaks are, by far, the number one cause of vintage engine piston seizures. I planned on a tune-up, MAF cleaner, fuel filter, air filter soon. If the EGR valve fails to close when EGR is not required, or if it leaks because of carbon buildup on the valve stem or valve seat, exhaust will be sucked into the intake manifold all the time creating a lean fuel mixture. The leak causes a venturi (sp?) effect as the exhaust gas passes by the leak. Logically, to me, i would think that an exhaust leak would cause the WB to be reading lean, however, im reading an excessively rich condition and it's not erratic either. To diagnose this leak we recommend applying air to the rear of the downstream converter or to the tail pipe on single systems @ 5psi to 8 psi. This is why leaks post-turbo show up as pig rich when on boost, but may also show as somewhat lean when off boostoff- boost sucking air in vs. I always thought I had a leak in the exhaust some where, I thought it was under the truck. 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). Then it started to shutter and loss power. If the leak is on the bottom side of the inlet gasket, it will often be necessary to remove the engine from the frame to see and accurately locate the leak. The most common cause is the crush washer seal in the exhaust port of the cylinder. Exhaust leaks can cause oxygen sensor to send a false lean reading. The high and low pressure waves will shift one way or the other inside the exhaust. and code still popped up running lean after a few miles. Before it warms to at least 600 deg F (315 deg C) it acts as an open circuit and when the ECM reads it, it reads the 450 mV bias. The leak causes a venturi (sp?) effect as the exhaust gas passes by the leak. The propane will be drawn into the site of the leak and the RPMs will rise. 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. DTC P0171 Fuel Trim System Lean Bank 1. The mixture becomes too lean to burn reliably in the combustion chamber. ) Vacuum leaks can cause a lean condition and/or possibly a high idle. Sharp Odor - The exhaust smell may be sharp and burn your nose. This can cause rough running, but may not be the cause of yours. If it comes back again, then check your o2 sensor conenctions and make sure they are clean and good. PHOTO 11 Whenever using a propane tool and tachometer to locate a vacuum leak or adjust the mixture, choose the rpm scale with the highest resolution (most graduations) for the most sensitive reading. Any exhaust leak can contibute a ping. A lean fuel mixture can cause an engine to have a surge or miss at idle and part throttle stumble on acceleration, leading to engine overheating and lack of power. The engine's intake system depends on being completely sealed and free from leaks. This is generally seen as a condition of running an engine too lean. Fuel contamination; Water, even in small amounts, can be delivered to the fuel injectors. So a leaking injector can cause a rich cylinder. The idle mixture screws will only effect the running at idle. This causes an incomplete burn which causes the fumes to explode in the exhaust system along with an audible pop or bang sound. The motor is a bored out 283 with corvette cams. The extra oxygen may come through a leak in the exhaust manifold gasket, an exhaust pipe sealing ring, or a damaged pipe. This may be due to a vacuum leak, but it can also be caused by a weak or inoperative accelerator pump in a carburetor, dirty injectors, or even ignition. If the exhuast leak is near or in front of the o2 sensor then it can let fresh air into the exhaust, and make the o2 sensor think it's running lean from the added o2 in the exhaust. Next we had to eliminate all the possible causes of a lean condition or excess oxygen in the exhaust. Fuel Pump problems causing a Lean Condition. Generally a dirty MAF will cause lean condition, and bad O2 sensors go rich. The additional air leaking into the exhaust may cause the oxygen sensor to report a lean condition and the ECU will inject more fuel. I planned on a tune-up, MAF cleaner, fuel filter, air filter soon. Because the air flow meter is reading one value, and the vacuum leak will cause the air/fuel mixture to get leaner, you do often get trouble codes about a lean mixture or misfire trouble codes. Note: If the spark burn lines for all the cylinders are higher than normal (indicating a lean fuel mixture), the underlying cause would be something that affects all cylinders such as an intake manifold leak, leaky vacuum hose, leaky EGR valve, leaky throttle gasket or low fuel. There are many things that can cause these trouble codes on the Cadillac Escalade. Typical to an intake manifold gasket that is leaking, is an engine misfire, especially with the engine cold. A lean condition, which can lead to the P0174 trouble code, is much more common than a rich condition. Page 3 of 4: Troubleshooting P0171 and P0174 (Ford 4. If there is an exhaust leak, the engine can cause outside air to be pulled into the exhaust and past the sensor. Exhaust leaks, especially near the sensor can pull in air and cause a false lean reading. Check for cracked hoses a bad gasket or a faulty EGR or PCV Valve. 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. The O2 sensors read/ send signals depending on the amount of "unburnt" air, so if air is being sucked in the exhaust the truck will keep adding fuel trying to fix the false signal that. If the leak is before the front O2 sensor, the additional air drawn in during light cruise will show the ECU a lean condition and your FT's will increase in the positive direction. If you want to fix this white smoke problem, the easy solution is to take your vehicle to the nearest auto body shop as soon as you notice it. The leak causes a venturi (sp?) effect as the exhaust gas passes by the leak. Fuel contamination; Water, even in small amounts, can be delivered to the fuel injectors. This causes an incomplete burn which causes the fumes to explode in the exhaust system along with an audible pop or bang sound. the owner said the donut seal might be crooked. 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. I once found a very small exhaust leak on an Oldsmobile, at a flanged exhaust pipe connection. Re: exhaust manifold leak: rough idle? I have a similar problem with my 88 302, the air check valve was completely melted, it sounded like an exhaust leak to. As a result, the PCM miscalculates the amount of the injected fuel, and the engine runs "lean". A rich mixture will cause the vehicle to run hot. Another common problem of this type is a single point seizure on the center of the exhaust side of the piston. An often overlooked condition is an intake leak. The term anal leakage would imply that the rectal contents are leaking out through the anus. This will cause the O2 sensor to signal lean and the ecu to add more fuel which will in fact make you rich. 7 TBI C/K Car Forums. Bubbles are seen in the radiator neck. Check vacuum at idle - should be 18-22 with a stock cam and lower with a more radical cam. 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). All it sees is air. Good catch. Low fuel pressure will reduce the fuel flow rate at the fuel injectors. Check the fuel pressure. A head gasket leak or cracked head will allow the coolant to be burned. What should I check next? Is this maybe a lean condition?. How much mileage, what's the condition of the catalytic converter, not often you see that code on that vehicle, Can be an intake leak, or cracked header flange causing an exhaust leak (very common). The problem is with the rubber grommets in the intake manifold bolts they will crack and cause an intake leak. Here's a list of the typical reasons for lean and rich situations. Low fuel pressure would affect all cylinders rather than an individual cylinder, as would most air leaks. Exhaust manifold leaks can be dangerous as well as cause other costly problems. I installed a new PCV valve when I did my new engine swap this spring. I have had plenty of drama with this kx100 eating top ends and discussed it here previousl. Absolutely, a leaking exhaust manifold can cause those codes. I put to much oil in my 2012 vw turbo but had some removed, the oil pressure rose to 220. The first step in diagnosing a p0171 lean code is to check for air or vacuum leaks. Water contamination will cause a lean condition. Most gasoline passenger and light duty trucks on the road today utilize electronically controlled fuel injection. 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. Check for proper air injection system operation. I am going to try the intake leak test again with propane. Otherwise you will need to use a air/fuel ratio measuring device like a pyrometer in the exhaust. 1 V due to the difference compared with the oxygen content of the ambient air. 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. As a result, the fuel/air mixture constantly fluctuates between rich and lean. Decreased Power and Acceleration. This can be caused by a dirty, clogged or inoperative fuel injector; air leaks; or low fuel pressure because of a weak pump, restricted filter or leaky pressure regulator. For an exhaust leak to be bad enough to throw off an oxygen sensor, the leak will be large enough where the smoke will be clearly visible. A leaking head gasket. In fact many cars will exhibit absolutely no misfires or idle speed roughness with the engine hot. In this article I am going to be discussing the 1. If reused it can cause an air leak that will cause a lean condition in the exhaust and thus the back firing. If there is an exhaust leak, the engine can cause outside air to be pulled into the exhaust and past the sensor. The air leak piston seizure, depending on the severity of the leak, can look like a four corner type or a lean mixture type of scoring pattern. They will look very white indicating higher temperature in the combustion chamber cause by a lean condition. Fuel contamination; Water, even in small amounts, can be delivered to the fuel injectors. All it sees is air. A throttle body/carbs that are out of sync can cause popping and uneven idling. Usually, carburated bikes run a little rich for safety, but if they are clogged it could cause a lean condition and an overheat. Fuel Pump problems causing a Lean Condition. If so, an exhaust leak upstream of the O2 sensors I believe makes the sensors think there's a lean condition so it causes the engine to run richer- this would mean worse fuel economy and worse emissions. We recommend Torque Pro. P0174 SATURN Tech Notes If the P0171 is combined with the P0174 code, it's very likely that the problem is caused by an intake leak. Take a look around and see if you can find the vacuum leak. A vacuum leak somewhere along bank 1 could cause a lean condition on that bank without effecting bank 2. A leak in the exhaust system before the O2 sensor will also cause incorrect readings. If the remaining oxygen content of the exhaust emission is 3 % (lean mixture), there is a voltage of 0. A very rough idle and poor acceleration sounds more like an intake leak. The O2 sensors read/ send signals depending on the amount of "unburnt" air, so if air is being sucked in the exhaust the truck will keep adding fuel trying to fix the false signal that. Something like a leaking injector oring, leaking air distribution manifold oring, or etc that is specific to bank 1. Every single one of them. An exhaust leak can trigger a Check Engine Light due to the fact that depending on the location of the leak, the. 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. This causes a big vacuum leak that permits extra "false air" to enter that cylinder resulting in a very lean condition. To diagnose this leak we recommend applying air to the rear of the downstream converter or to the tail pipe on single systems @ 5psi to 8 psi. If the code returns, continue with your diagnosis. Here's a great YouTube video on how to find a vacuum leak. Excessive engine oil consumption: causes, common problems, consequences, troubleshooting. It will cause a drop in performance, and if it's two stroke can lead to engine seizure. Re: Can exhaust leak cause P0171 and P0174 Not unless theleak is at the exhaust manifold gasket right at the head. Airflow sensor, fuel pressure, or things common to both banks will not trigger a single bank code. One common yet serious concern is a flue pipe that is leaking water or condensation, or even gas. These can often cause inconsistent problems and conditions. Whether it happens in the intake or exhaust, the loud noise that results can be momentarily startling to the rider and those nearby. Could the exhaust leaking right at the head pipe cause a lean condition?. A leaking head gasket. A very rough idle and poor acceleration sounds more like an intake leak. 5 liter engine used in the Camry, Avalon, Solara and Sienna van. it was talking about modern cars where an exhaust leak can not cause a burnt valve due to the computer compensating for the lean condition caused by an incorrect oxygen sensor reading in the exhaust on a modern car which in turn riches the intake. All it sees is air. Another cause of blue smoke is bad valve stem seals. I sprayed it out with carb cleaner, but did not actually test operation. The P0171 is one of the more common trouble codes. The most likely cause of a lean condition is a vacuum leak. Use GM part # 12346004, Teflon pipe sealant (for high heat), or Locktite 272 (hi heat) to lock the exhaust manifold bolts into the head. When an engine that has computer controlled spark and fuel systems has a vacuum leak, the following events occur. Monday after having the tires rotated and balanced I took the truck to a exhaust shop for a free inspection, the guy said it was leaking from the drivers side exhaust manifld but he couldnt tell if it was t. Then have a helper start the engine and hold the idle at about 1500 rpm. This lean mixture can quickly result in a seized piston. An intake leak will not be limited to just the manifold seals. Ford TSB 04-17-4 details procedures for checking fuel trim and looking for vacuum leaks. 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. This is called "accelerator pump" logic or tip in enrichment. Double up some cardboard and stop up the exhaust with gloves on, if its leaking at the pipe you should here it and as T Q said if its a blown head gasket you should have a dead miss or that cylinder would be cooler to the touch and possibly be pumping some oil out also, good Luck and let us know what u find, Capital Jack. An exhaust leak may cause outside air to enter the exhaust gas stream going past the O2 sensor, causing the system to appear lean. 1 V due to the difference compared with the oxygen content of the ambient air. This condition where the bike does not get enough fuel and too much air can cause a furnace effect. Can an exhause leak cause the 171 lean condition code to appear?. Fix it? Richen your fuel mixture or replace the original exhaust or get one suited to that bike. 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:.