Cylinder 4 Misfire
07-01-2011, 08:06 AM
#11
AudiWorld Super User
Sounds like you need to smoke it out.
http://www.popularmechanics.com/cars...-a-vacuum-leak
The tool is quite expensive so find a mechanic or try fabbing one up. I wonder if fog oil from a halloween smoke machine would work...
http://www.popularmechanics.com/cars...-a-vacuum-leak
The tool is quite expensive so find a mechanic or try fabbing one up. I wonder if fog oil from a halloween smoke machine would work...
07-04-2011, 04:27 PM
#12
AudiWorld Senior Member
Thread Starter
Ok guys - I'm sorry if I haven't tried all of the suggestions given at this point - but my experimenting just hasn't lead me down those roads yet. I know that I hate it when I read threads from people who get good advice and don't listen...so I'm sorry if I'm being that guy.
I have been going through the vacuum lines as best I can now that the engine is all back together, and I did find one small hose that was broken. Down by the EGT sensors and the bottom of the spider hose, there are two connections with 3 hoses going in a kind of peace sign pattern. There is a short hose that comes off one of these tees, and goes directly under the EGTs into a metal pipe. This is the ONLY braided hose that I did NOT replace while I had the engine apart with the blue silicone tubing I got from ECS. I didn't replace it because it was on a plastic T with two of those one-time use clamps and I was afraid I would break the T while I tried to take it off. Well, I couldn't see it, but reaching in and feeling and pulling on the hose a little opened up a huge hole. So I replaced this hose with more silicone tubing.
For about 10 seconds, the car seemed to run much better and idle better. The SAI pump actually came on while it was warming up and growled a bit longer than it was. Then it started doing the same thing again!!!
The misfire on cylinder 4 has gone down quite a bit, and I'm feeling that the SAI flow too low codes were being thrown by the hose I replaced, since the one section went to a metal pipe under the intake, and the other two parts of the T went to each of the metal lines that go to the combi valves I think.
In looking through the vag-com, however, I keep getting drawn back to measuring block #1 in the engine module. The two boxes to the left measure "Lambda Control Bank 1" and "Bank 2". Bank 1 reads about 3.X% and Bank 2 (the bank with the misfire) reads about 13.X%.
I checked this on my car and both read 0.0%.
Could this cause a rough idle and misfire?? I'm looking at X19's suggestion and thinking that if the O2 is telling the car I have a lean condition, the car would be sending more fuel into the engine, which would then cause a misfire and bad idle maybe? If I don't really have a lean condition, and the O2 sensor is just giving a false reading - then it seems like the effects would be similar to that of a vacuum leak??? Or am I way off or over-thinking this?
Also, the engine has a slight tick, tick, tick noise when it runs. I started trying to find this (at first it sounded like it was at the front of the engine bay) - but I used the good ol' rubber tubing method and narrowed it down, I believe, to the fuel injector on cylinder #3. I put the hose on top of the electrical connector to this injector and it gets very loud. The noise travels through the fuel lines feeding the rail, but it's loudest at the injector #3.
There is also a valve to the middle of the engine bay near injector #3 that makes a small ticking noise, like the valve is constantly opening and closing.
Am I over thinking this? Should I keep searching for more vacuum leaks? I know it's not the Spider hose, the SAI pump hose, and I have replaced all of the braided line with brand new silicone tubing....
Thanks for the help guys.
I have been going through the vacuum lines as best I can now that the engine is all back together, and I did find one small hose that was broken. Down by the EGT sensors and the bottom of the spider hose, there are two connections with 3 hoses going in a kind of peace sign pattern. There is a short hose that comes off one of these tees, and goes directly under the EGTs into a metal pipe. This is the ONLY braided hose that I did NOT replace while I had the engine apart with the blue silicone tubing I got from ECS. I didn't replace it because it was on a plastic T with two of those one-time use clamps and I was afraid I would break the T while I tried to take it off. Well, I couldn't see it, but reaching in and feeling and pulling on the hose a little opened up a huge hole. So I replaced this hose with more silicone tubing.
For about 10 seconds, the car seemed to run much better and idle better. The SAI pump actually came on while it was warming up and growled a bit longer than it was. Then it started doing the same thing again!!!
The misfire on cylinder 4 has gone down quite a bit, and I'm feeling that the SAI flow too low codes were being thrown by the hose I replaced, since the one section went to a metal pipe under the intake, and the other two parts of the T went to each of the metal lines that go to the combi valves I think.
In looking through the vag-com, however, I keep getting drawn back to measuring block #1 in the engine module. The two boxes to the left measure "Lambda Control Bank 1" and "Bank 2". Bank 1 reads about 3.X% and Bank 2 (the bank with the misfire) reads about 13.X%.
I checked this on my car and both read 0.0%.
Could this cause a rough idle and misfire?? I'm looking at X19's suggestion and thinking that if the O2 is telling the car I have a lean condition, the car would be sending more fuel into the engine, which would then cause a misfire and bad idle maybe? If I don't really have a lean condition, and the O2 sensor is just giving a false reading - then it seems like the effects would be similar to that of a vacuum leak??? Or am I way off or over-thinking this?
Also, the engine has a slight tick, tick, tick noise when it runs. I started trying to find this (at first it sounded like it was at the front of the engine bay) - but I used the good ol' rubber tubing method and narrowed it down, I believe, to the fuel injector on cylinder #3. I put the hose on top of the electrical connector to this injector and it gets very loud. The noise travels through the fuel lines feeding the rail, but it's loudest at the injector #3.
There is also a valve to the middle of the engine bay near injector #3 that makes a small ticking noise, like the valve is constantly opening and closing.
Am I over thinking this? Should I keep searching for more vacuum leaks? I know it's not the Spider hose, the SAI pump hose, and I have replaced all of the braided line with brand new silicone tubing....
Thanks for the help guys.
07-05-2011, 03:52 AM
#15
AudiWorld Senior Member
Thread Starter
Car has been warmed up and run for quite some time. The SAI pump only runs when the car is cold.
This is the new head, which went through a refurbishing process, and the cams looked fine to me and to a machine shop guy who finally came over and helped me put it together. I am also getting very good compression on this cylinder, which I believe suggests the valves are opening and shutting as they should be.
This is the new head, which went through a refurbishing process, and the cams looked fine to me and to a machine shop guy who finally came over and helped me put it together. I am also getting very good compression on this cylinder, which I believe suggests the valves are opening and shutting as they should be.
07-05-2011, 08:23 AM
#16
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Still sounds like fuel to me. During warmup extra fuel is injected and the sai adds air so the catalytic convertor can burn it. So probably that injector or it's driver in the ECM is bad. Or the cable to the ECM.
During warmup there is enough fuel to fire and so you don't get the misfire fault. Then when warm the duty cycle goes down and now there is not enough fuel.
During warmup there is enough fuel to fire and so you don't get the misfire fault. Then when warm the duty cycle goes down and now there is not enough fuel.
07-05-2011, 09:51 AM
#17
AudiWorld Senior Member
Thread Starter
69G- My thinking is...if it is fuel, why is ONLY one cylinder misfiring. This is pretty consistent ...up to 18 misfires on the 4th cylinder and 0 across all others. This is what is throwing me.
I could see if it was a fuel injector, but I swapped them and got the same result. Even my O2 theory seems off to me...I would think the entire bank would be misfiring.
The only other thought I have is that maybe the cylinder that fires before Cyl. 4 is off and retarding Cyl. 4 somehow, but this seems to be a stretch. I believe this is Cylinder #1.
I can't believe I can't figure this one out...
If I have time I'll swap the ECM and take the O2's outta my car...didn't wanna go through having to dig out an O2 from the front of the cats on a hunch, but I'm going to.
I could see if it was a fuel injector, but I swapped them and got the same result. Even my O2 theory seems off to me...I would think the entire bank would be misfiring.
The only other thought I have is that maybe the cylinder that fires before Cyl. 4 is off and retarding Cyl. 4 somehow, but this seems to be a stretch. I believe this is Cylinder #1.
I can't believe I can't figure this one out...
If I have time I'll swap the ECM and take the O2's outta my car...didn't wanna go through having to dig out an O2 from the front of the cats on a hunch, but I'm going to.
07-05-2011, 08:09 PM
#18
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69G- My thinking is...if it is fuel, why is ONLY one cylinder misfiring. This is pretty consistent ...up to 18 misfires on the 4th cylinder and 0 across all others. This is what is throwing me.
I could see if it was a fuel injector, but I swapped them and got the same result. Even my O2 theory seems off to me...I would think the entire bank would be misfiring.
The only other thought I have is that maybe the cylinder that fires before Cyl. 4 is off and retarding Cyl. 4 somehow, but this seems to be a stretch. I believe this is Cylinder #1.
I can't believe I can't figure this one out...
If I have time I'll swap the ECM and take the O2's outta my car...didn't wanna go through having to dig out an O2 from the front of the cats on a hunch, but I'm going to.
I could see if it was a fuel injector, but I swapped them and got the same result. Even my O2 theory seems off to me...I would think the entire bank would be misfiring.
The only other thought I have is that maybe the cylinder that fires before Cyl. 4 is off and retarding Cyl. 4 somehow, but this seems to be a stretch. I believe this is Cylinder #1.
I can't believe I can't figure this one out...
If I have time I'll swap the ECM and take the O2's outta my car...didn't wanna go through having to dig out an O2 from the front of the cats on a hunch, but I'm going to.
07-06-2011, 12:48 AM
#19
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