Cylinder misfire audi
#1
07-28-2013, 10:45 PM
Cylinder misfire audi
CYLIDER MISFIRE ON STARTUP, Then runs fine
I receive many inquiries on this so I wanted to post a thread to help out with the diagnosis. Just in case your symptoms are a little different I included some other stuff to look into. Diagnosis is not a method of fortune telling however i do offer those services for a fee, individual results may vary...
Remember If you solve your problems post your resolutions so others can benefit.The Audi brotherhood is here to help you, but please pass it on to others!
I'll go through a diagnostic list but, you'll still have to do some research if you don't know how to perform certain tests. So I'll presume you know your way around an engine or google or both.
My 2002 A6 3.0 had a misfire on cylinder 4 at startup, Using a vagcom I found it misfiring 30-40 times but you could feel the bumble from the engine for 20 seconds or so. Following this it ran fine. Never had smoke or vapor from the tail pipe.
You may have a code "P0304" misfire cylinder 4 or what ever cylinder.
The last number depicts the cylinder misfiring, in this case "4"
Also other codes may be set because of this issue. The computer will attempt to compensate for the problem and these measure will effect other systems, like running rich or lean creating more problems and setting more codes.
This problem is most likely something leaking into the cylinder or a loose spark plug but you never know so...
What is happening; The cylinder fails to fire or fires late or early and this causes a knock (a sharp vibration) that is picked up by a Knock sensor.
A knock sensor is a crystal that when compressed will allow current to flow through it. They rarely go bad, but if they are overtightened will give poor readings. The 3.0 has 1 per bank, so if you only have one cylinder misfiring that knock sensor isn't it. Because if it were bad it would register all 3 cylinders all of the time or non of the time, and most likely not report a knock. A knock reported to the Computer is registered as a misfire. Because the word Knock is a bad word in the auto industry.
Lets get started...
1) check your coil pack and spark plug.
coil pack could be going bad, spark plug could be loose or bad
remove the coil pack and plug from the bad cylinder and swap it with a known good cylinder.(replace the spark plug if you can with a new one). see if the problem moves to another cylinder. If it does it's the coil pack or plug.
Also be certain that there is no oil buildup down the coil tube, due to leaking valve cover gaskets. This can cause problems, so replace the gaskets if you see a puddle of oil down there.
Sometimes if a spark plug is loose the engine heat will cause the head to expand and seal it after 15 minutes or so. but the car will continue to run a little rough. But I've seen it before so it does happen.
If the problem moves to another cylinder your coil pack or spark plug was bad if not proceed to no 2
2) Check for fluid in the cylinder.
The car must be cold and it would be best if it sits overnight, so the cylinder fills with fluid.
Remove the spark plug from the misfiring cylinder get a very long white pipe cleaner or something similar and slide it down into the tube, through the spark plug hole to the bottom of the cylinder. Holding one end in your hand of course, don't push the whole thing in there, how will you get it out. You want to angle it to the lower portion of the cylinder to dip into any fluid that might be collecting in there. All fluid will be dark, there is carbon in there so don't judge the liquid by color.
determine if it is oil, coolant, or fuel
If you have been loosing coolant and see a vapor haze from the exhaust this could be the reason. If it's oil you won't really smell it burning because the cats will pick it up and burn it off. It will only be a tea spoon amount at best and maybe slightly more if it is fuel.
If it is coolant- you have a leak in the head gasket and you can try adding a quart of bars leak head gasket sealant, it has silicate and will glass pack the leak when the cylinder ignites. The latest generation silicate from bars or other manufacturers can be left in the system. Any auto store has it. I use the bars and it works so...
If it is OIL, That sucks because your valve seals are leaking and although the seals are a buck a piece the rest of the gaskets and o-rings and head bolts tools, etc... will set you back well over a grand and 3 of the longest work days you've seen in a long time (providing you order all of the parts you need on the first shot and know how to rebuild heads).You will need to do them all, both sides, because if 1 is bad they are all just about done. It's a nightmare, The seals can be replaced with the heads on but the tools to do that are expensive as well and if you loose a valve clip some where you'll be forever wondering where it went. I pulled my heads because this was my problem, OH, I loved doing it, I liken it a man giving his wife an std after a bachelor party in Vegas! That wasn't me BTW...
If it's fuel, then it's a bad injector that is not sealing and leaking when the car is off. This may also be accompanied by a host of other codes, because that cylinder will be running rich most of the time. If this is the case then the injector needs to be replaced, not a bad job at all. Just be certain to rub some grease on the injector o rings so you don't tear or roll them when you push them all back in.
You can also do a fuel pressure test to determine if the system is maintaining pressure or loosing it right away. It will loose pressure when the ignition is off but not for at least 10-15 minutes or so. If it looses pressure fast then, something is wrong and the fuel is going somewhere! But remember seeing is believing. It is better to see it leak and know then think it's leaking and waste money replacing parts that were never bad.
You can also pull the rail while leaving the injectors in the rail and pressurize the system by turning the key to on to see if any are leaking. Put a towel under them to catch any fuel, do not let it accumulate on electronic components and possibly ignite.
If you want to make sure they are all spraying an equal volume, I have done this by placing small vessels over each injector and cranking over the engine and measuring the fuel volume in each vessel. However this sets all sorts of codes in the ECM, because it will want to compensate for the engine not firing at all. What this may do is cause the system to run rich on the next startup, or cut the fuel to prevent flooding. So disconnect your battery or reset the parameters with a vagcom prior to next startup.
If That's not it and you have nothing in the cylinder go to 3
3) There is a possibility that your injector is not firing,
you may check these with a small two lead led installed/clipped inline at the injector terminal or a set of "NOIDS" if it flashes each time then you have power going to the injector and an injector that is not opening when charged.
Pull the injector attach a 9 volt battery across the two terminals and you will hear it click. You can try soaking it overnight in sea foam.pen the injector with the 9 volt battery and blow through it with compressed air or just replace the injector.
If you are not positive you can also swap the injector with one from a known good cylinder just like the coil pack , and see if the problem moves. If it does, it's the injector if it doesn't then you need to check the power going to the injector.
The above problems with the injector will tend to be persistent or intermittent not something that only happens on start up.
be certain you clean and inspect the terminals for a tight connection.
If that's not it go to no.4
4) You may have a problem in the wiring harness to the coil pack,
but this won't go away on start up it will be persistent or intermittent. They are a PITA to find, look for loose exposed wires, burnt wires, pinched wires loose connectors.
Connectors, and terminals, clean the male terminals with a nail file, then put the nail file (dirty and all) back into the wife's makeup kit so she knows you been working hard on her friggin audi again.
If you can pinch the female terminals closed a bit by easily prying them back together with a small pick or dentist tool. I apply a liberal amount of di-electric grease on my terminals and have excellent results. Buy it in a tube for 3 bucks at any auto store.
Still not it, and you didn't mess up on any of the above tests.
you should double check the above and make sure you did them right.
goto 5
5) It is possible that you have a problem with the ECM,
engine control module, the engine computer, , performance control unit, what ever you want to call it but Audi calls it the ECM
For some reason the ECM has been mentioned on several TSB's that it could be messing around with a cylinder on startup, testing this would require a vagcom, and a bosche addon. I would follow the cylinder on startup and watch the fuel ratio etc to see whats happening there. Outside of that, get it flashed. Finding a problem with that thing is for someone with time to kill and no life to worry about.
There are a few TSB's on ECM issues that require re flashing. Due to issues of a cylinder misfire on start-up. However I'll bet the flash just turns the knock sensor recognition off to that cylinder on startup or the code off to that cylinder because they couldn't finger out the problem nor wanted to spend the money repairing it. They wouldn't tell us if that were the case so don't ask. Why, well because that ladies and gentlemen would be illegal.
If you don't think it's the ECM or if your problem is intermittent or persistent.
The problem starts happening anytime or all the time. It could still be some of the above or...
A) Perform a cylinder leak down test, to determine a bad head gasket or valve or a crack in the head or block. But a crack may not let compression escape if it gets sealed up by the fluid leaking through it. But it would most likely be best to search for a crack with the engine both cold and hot. Also a crack will have all sorts of other issues. Milky oil and carbon in the coolant. smoke and or vapor from the tail pipe.
B) Pull the valve covers and have a peak at the lobes on the cams of that cylinder for excessive wear. This will be accompanied by a lot of engine tapping.
C) Inspect the Lifters for a collapsed lifter or a worn through lifter, also accompanied by annoying tapping and badly worn cam lobes.
D) If you are constantly burning oil, that is a more serious issue than anything covered here, could be many things, bad rings, cracks... who knows.
E) if a whole bank is off and doing the dance, check the Timing belt, valves harnesses etc...
Definition;
Audi Brotherhood, An Audi brother is easily recognized.
He will have an Audi on jackstands various occasions throughout the year.
Signed into the order by bloody knuckles, a greased up chin and potty mouth remarks about the inaccessibility to bolts the part he needs to replace.
Usually "drive it like you stole it" is a phrase only used while joyriding in a friends Audi or on a test drive.
Often accompanied by a wife that has Honda brochures in her pocketbook at all times.
If you see a brother, never ask him how his car is running. This is bad juju and frowned upon. The rings mean-----SHHHHHHHHHHHH!!!!! for a reason.
I hope this helps those who have these issues.
as you work on your car, don't forget to order vac lines to replace old rotted vacuum lines and hoses that break when you look at them. clean-up terminals when you are near them. Cable tie terminals back together tightly if they break when disconnecting them.
It is extremely helpful if you have a Bentleypublishers Audi repair manual to guide you through the installation process. However this particular problem isn't fully covered there. Bentley Publishers Home - Bentley Publishers - Repair Manuals and Automotive Books
I receive many inquiries on this so I wanted to post a thread to help out with the diagnosis. Just in case your symptoms are a little different I included some other stuff to look into. Diagnosis is not a method of fortune telling however i do offer those services for a fee, individual results may vary...
Remember If you solve your problems post your resolutions so others can benefit.The Audi brotherhood is here to help you, but please pass it on to others!
I'll go through a diagnostic list but, you'll still have to do some research if you don't know how to perform certain tests. So I'll presume you know your way around an engine or google or both.
My 2002 A6 3.0 had a misfire on cylinder 4 at startup, Using a vagcom I found it misfiring 30-40 times but you could feel the bumble from the engine for 20 seconds or so. Following this it ran fine. Never had smoke or vapor from the tail pipe.
You may have a code "P0304" misfire cylinder 4 or what ever cylinder.
The last number depicts the cylinder misfiring, in this case "4"
Also other codes may be set because of this issue. The computer will attempt to compensate for the problem and these measure will effect other systems, like running rich or lean creating more problems and setting more codes.
This problem is most likely something leaking into the cylinder or a loose spark plug but you never know so...
What is happening; The cylinder fails to fire or fires late or early and this causes a knock (a sharp vibration) that is picked up by a Knock sensor.
A knock sensor is a crystal that when compressed will allow current to flow through it. They rarely go bad, but if they are overtightened will give poor readings. The 3.0 has 1 per bank, so if you only have one cylinder misfiring that knock sensor isn't it. Because if it were bad it would register all 3 cylinders all of the time or non of the time, and most likely not report a knock. A knock reported to the Computer is registered as a misfire. Because the word Knock is a bad word in the auto industry.
Lets get started...
1) check your coil pack and spark plug.
coil pack could be going bad, spark plug could be loose or bad
remove the coil pack and plug from the bad cylinder and swap it with a known good cylinder.(replace the spark plug if you can with a new one). see if the problem moves to another cylinder. If it does it's the coil pack or plug.
Also be certain that there is no oil buildup down the coil tube, due to leaking valve cover gaskets. This can cause problems, so replace the gaskets if you see a puddle of oil down there.
Sometimes if a spark plug is loose the engine heat will cause the head to expand and seal it after 15 minutes or so. but the car will continue to run a little rough. But I've seen it before so it does happen.
If the problem moves to another cylinder your coil pack or spark plug was bad if not proceed to no 2
2) Check for fluid in the cylinder.
The car must be cold and it would be best if it sits overnight, so the cylinder fills with fluid.
Remove the spark plug from the misfiring cylinder get a very long white pipe cleaner or something similar and slide it down into the tube, through the spark plug hole to the bottom of the cylinder. Holding one end in your hand of course, don't push the whole thing in there, how will you get it out. You want to angle it to the lower portion of the cylinder to dip into any fluid that might be collecting in there. All fluid will be dark, there is carbon in there so don't judge the liquid by color.
determine if it is oil, coolant, or fuel
If you have been loosing coolant and see a vapor haze from the exhaust this could be the reason. If it's oil you won't really smell it burning because the cats will pick it up and burn it off. It will only be a tea spoon amount at best and maybe slightly more if it is fuel.
If it is coolant- you have a leak in the head gasket and you can try adding a quart of bars leak head gasket sealant, it has silicate and will glass pack the leak when the cylinder ignites. The latest generation silicate from bars or other manufacturers can be left in the system. Any auto store has it. I use the bars and it works so...
If it is OIL, That sucks because your valve seals are leaking and although the seals are a buck a piece the rest of the gaskets and o-rings and head bolts tools, etc... will set you back well over a grand and 3 of the longest work days you've seen in a long time (providing you order all of the parts you need on the first shot and know how to rebuild heads).You will need to do them all, both sides, because if 1 is bad they are all just about done. It's a nightmare, The seals can be replaced with the heads on but the tools to do that are expensive as well and if you loose a valve clip some where you'll be forever wondering where it went. I pulled my heads because this was my problem, OH, I loved doing it, I liken it a man giving his wife an std after a bachelor party in Vegas! That wasn't me BTW...
If it's fuel, then it's a bad injector that is not sealing and leaking when the car is off. This may also be accompanied by a host of other codes, because that cylinder will be running rich most of the time. If this is the case then the injector needs to be replaced, not a bad job at all. Just be certain to rub some grease on the injector o rings so you don't tear or roll them when you push them all back in.
You can also do a fuel pressure test to determine if the system is maintaining pressure or loosing it right away. It will loose pressure when the ignition is off but not for at least 10-15 minutes or so. If it looses pressure fast then, something is wrong and the fuel is going somewhere! But remember seeing is believing. It is better to see it leak and know then think it's leaking and waste money replacing parts that were never bad.
You can also pull the rail while leaving the injectors in the rail and pressurize the system by turning the key to on to see if any are leaking. Put a towel under them to catch any fuel, do not let it accumulate on electronic components and possibly ignite.
If you want to make sure they are all spraying an equal volume, I have done this by placing small vessels over each injector and cranking over the engine and measuring the fuel volume in each vessel. However this sets all sorts of codes in the ECM, because it will want to compensate for the engine not firing at all. What this may do is cause the system to run rich on the next startup, or cut the fuel to prevent flooding. So disconnect your battery or reset the parameters with a vagcom prior to next startup.
If That's not it and you have nothing in the cylinder go to 3
3) There is a possibility that your injector is not firing,
you may check these with a small two lead led installed/clipped inline at the injector terminal or a set of "NOIDS" if it flashes each time then you have power going to the injector and an injector that is not opening when charged.
Pull the injector attach a 9 volt battery across the two terminals and you will hear it click. You can try soaking it overnight in sea foam.pen the injector with the 9 volt battery and blow through it with compressed air or just replace the injector.
If you are not positive you can also swap the injector with one from a known good cylinder just like the coil pack , and see if the problem moves. If it does, it's the injector if it doesn't then you need to check the power going to the injector.
The above problems with the injector will tend to be persistent or intermittent not something that only happens on start up.
be certain you clean and inspect the terminals for a tight connection.
If that's not it go to no.4
4) You may have a problem in the wiring harness to the coil pack,
but this won't go away on start up it will be persistent or intermittent. They are a PITA to find, look for loose exposed wires, burnt wires, pinched wires loose connectors.
Connectors, and terminals, clean the male terminals with a nail file, then put the nail file (dirty and all) back into the wife's makeup kit so she knows you been working hard on her friggin audi again.
If you can pinch the female terminals closed a bit by easily prying them back together with a small pick or dentist tool. I apply a liberal amount of di-electric grease on my terminals and have excellent results. Buy it in a tube for 3 bucks at any auto store.
Still not it, and you didn't mess up on any of the above tests.
you should double check the above and make sure you did them right.
goto 5
5) It is possible that you have a problem with the ECM,
engine control module, the engine computer, , performance control unit, what ever you want to call it but Audi calls it the ECM
For some reason the ECM has been mentioned on several TSB's that it could be messing around with a cylinder on startup, testing this would require a vagcom, and a bosche addon. I would follow the cylinder on startup and watch the fuel ratio etc to see whats happening there. Outside of that, get it flashed. Finding a problem with that thing is for someone with time to kill and no life to worry about.
There are a few TSB's on ECM issues that require re flashing. Due to issues of a cylinder misfire on start-up. However I'll bet the flash just turns the knock sensor recognition off to that cylinder on startup or the code off to that cylinder because they couldn't finger out the problem nor wanted to spend the money repairing it. They wouldn't tell us if that were the case so don't ask. Why, well because that ladies and gentlemen would be illegal.
If you don't think it's the ECM or if your problem is intermittent or persistent.
The problem starts happening anytime or all the time. It could still be some of the above or...
A) Perform a cylinder leak down test, to determine a bad head gasket or valve or a crack in the head or block. But a crack may not let compression escape if it gets sealed up by the fluid leaking through it. But it would most likely be best to search for a crack with the engine both cold and hot. Also a crack will have all sorts of other issues. Milky oil and carbon in the coolant. smoke and or vapor from the tail pipe.
B) Pull the valve covers and have a peak at the lobes on the cams of that cylinder for excessive wear. This will be accompanied by a lot of engine tapping.
C) Inspect the Lifters for a collapsed lifter or a worn through lifter, also accompanied by annoying tapping and badly worn cam lobes.
D) If you are constantly burning oil, that is a more serious issue than anything covered here, could be many things, bad rings, cracks... who knows.
E) if a whole bank is off and doing the dance, check the Timing belt, valves harnesses etc...
Definition;
Audi Brotherhood, An Audi brother is easily recognized.
He will have an Audi on jackstands various occasions throughout the year.
Signed into the order by bloody knuckles, a greased up chin and potty mouth remarks about the inaccessibility to bolts the part he needs to replace.
Usually "drive it like you stole it" is a phrase only used while joyriding in a friends Audi or on a test drive.
Often accompanied by a wife that has Honda brochures in her pocketbook at all times.
If you see a brother, never ask him how his car is running. This is bad juju and frowned upon. The rings mean-----SHHHHHHHHHHHH!!!!! for a reason.
I hope this helps those who have these issues.
as you work on your car, don't forget to order vac lines to replace old rotted vacuum lines and hoses that break when you look at them. clean-up terminals when you are near them. Cable tie terminals back together tightly if they break when disconnecting them.
It is extremely helpful if you have a Bentleypublishers Audi repair manual to guide you through the installation process. However this particular problem isn't fully covered there. Bentley Publishers Home - Bentley Publishers - Repair Manuals and Automotive Books
#3
08-16-2014, 03:03 PM
Great write up.
I'm currently going through my own misfire torture. My whole left/drivers side bank (4,5,6) is misfiring.
It isn't the timing, I have the cam locking bar and the crank pin and have triple checked this.
It isn't the injectors. All connectors are reading the same voltage, all the injectors are reading 16.6 to 16.8 ohms and I swapped the injectors over from the other bank with no change.
I swapped over the spark plugs, which are all new, from the other bank with no change.
I swapped over the HT leads from the other bank with no change.
I fitted a new cam position sensor with no change
I managed to turn each coil around on it's bracket then connected the HT leads to their opposite connection with no change. I did this one to see if one side of the coils were going bad.
I ran compression tests on all cylinders. All cylinders were 160 to 170 PSI and reached their maximum pressure in 5 cycles. It may have been 4 cycles but I wanted to be sure they were at max.
I noticed that some of the bolts were loose on the intake housing. Tightening them made no difference.
I've had someone suggest that I pull the upstream o2 sensor from that side to rule out a plugged cat. I has been sat for sometime with the heads off so it isn't impossible that a rodent nested in there over the winter. Back pressure wouldn't cause misfire though would it?
Also, occasionally, and just for 10 seconds or so it will idle with out missing, then go back to sounding like I have a hole in my drivers side headers.
I also did a full cylinder head rebuild. All gaskets, seals, bolts. I also had the heads skimmed flat and had the valves and seats reground. Besides throwing all its coolant out of the exhaust, it ran fine before I pulled it apart
I'm frustrated beyond belief and any other ideas of things to check will be much appreciated.
I'm currently going through my own misfire torture. My whole left/drivers side bank (4,5,6) is misfiring.
It isn't the timing, I have the cam locking bar and the crank pin and have triple checked this.
It isn't the injectors. All connectors are reading the same voltage, all the injectors are reading 16.6 to 16.8 ohms and I swapped the injectors over from the other bank with no change.
I swapped over the spark plugs, which are all new, from the other bank with no change.
I swapped over the HT leads from the other bank with no change.
I fitted a new cam position sensor with no change
I managed to turn each coil around on it's bracket then connected the HT leads to their opposite connection with no change. I did this one to see if one side of the coils were going bad.
I ran compression tests on all cylinders. All cylinders were 160 to 170 PSI and reached their maximum pressure in 5 cycles. It may have been 4 cycles but I wanted to be sure they were at max.
I noticed that some of the bolts were loose on the intake housing. Tightening them made no difference.
I've had someone suggest that I pull the upstream o2 sensor from that side to rule out a plugged cat. I has been sat for sometime with the heads off so it isn't impossible that a rodent nested in there over the winter. Back pressure wouldn't cause misfire though would it?
Also, occasionally, and just for 10 seconds or so it will idle with out missing, then go back to sounding like I have a hole in my drivers side headers.
I also did a full cylinder head rebuild. All gaskets, seals, bolts. I also had the heads skimmed flat and had the valves and seats reground. Besides throwing all its coolant out of the exhaust, it ran fine before I pulled it apart
I'm frustrated beyond belief and any other ideas of things to check will be much appreciated.
Last edited by Brityank; 08-16-2014 at 03:12 PM.
#4
08-17-2014, 01:12 PM
I just wanted to let you know that I solved my problem.
It was big air leak. The egr gasket was leaking. I stalled the motor when checking for air/vacuum leaks with carb cleaner. It runs great now, but I'm glad that I know what else to look for now, thanks to articles like this one.
It was big air leak. The egr gasket was leaking. I stalled the motor when checking for air/vacuum leaks with carb cleaner. It runs great now, but I'm glad that I know what else to look for now, thanks to articles like this one.
#5
05-02-2016, 03:03 PM
Brityank
I know this is an old post however I figured I'd ask anyways.
Basics: 2010 3.0T 67k miles
I'm having somewhat similar issues. The car was running fine, I go away on holiday for 2.5 weeks, come back, start the car up, it runs for about 20-30 seconds then sputters and dies. I can keep it going if I give gas but the moment I let go, car dies. All the while I can hear/feel it misfiring. Car starts up without issue. Just after the 20 seconds or so then it start misfiring.
I check codes and it's misfiring in 4,5,6. Cylinders 1,2,3 in bank1 aren't having any issues.
Swapped and then replaced plugs and coil packs and problem stays in the same bank. Replaced oil filter and battery in the meantime as well. Compression tests in all cylinders come about same as yours ~180 for all.
Was the car in use up until when the issue happened or did it sit for some time such as mine for a couple of weeks? When you say the EGR gasket was leaking, I'm assuming it just corroded away? And all you did was replace the gasket?
Car is in indy shop now. They originally thought it was carbon buildup but said they took it apart and that's not the issue.
thanks in advance for any input.
I know this is an old post however I figured I'd ask anyways.
Basics: 2010 3.0T 67k miles
I'm having somewhat similar issues. The car was running fine, I go away on holiday for 2.5 weeks, come back, start the car up, it runs for about 20-30 seconds then sputters and dies. I can keep it going if I give gas but the moment I let go, car dies. All the while I can hear/feel it misfiring. Car starts up without issue. Just after the 20 seconds or so then it start misfiring.
I check codes and it's misfiring in 4,5,6. Cylinders 1,2,3 in bank1 aren't having any issues.
Swapped and then replaced plugs and coil packs and problem stays in the same bank. Replaced oil filter and battery in the meantime as well. Compression tests in all cylinders come about same as yours ~180 for all.
Was the car in use up until when the issue happened or did it sit for some time such as mine for a couple of weeks? When you say the EGR gasket was leaking, I'm assuming it just corroded away? And all you did was replace the gasket?
Car is in indy shop now. They originally thought it was carbon buildup but said they took it apart and that's not the issue.
thanks in advance for any input.
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