Definitive guide to fixing secondary air injection incorrect flow detected problems.
10-25-2005, 01:46 PM
#1
AudiWorld Super User
Thread Starter
Definitive guide to fixing secondary air injection incorrect flow detected problems.
Secondary air injection seems to be something sooner or later every Audi owner has a problem with. Let me run down the symptoms and then the steps to fix them. This should be the definitive guide on how to repair the system. If you had an issue & repair that wasn't covered by this guide, please shoot me an email.
The first and most common problem is broken/frayed vacuum lines that run to the kombi valve(s). If you have a 2.8, there was a recall on most of them to update the vacuum lines to beefier lines. If this wasn't you, or you have a 1.8, it's still easy to check the vacuum lines. If they even look suspect, just replace them. Vacuum hose is cheap enough and easy to change out. Vacuum lines don't last forever, and heat/age will wear them out.
The next thing to check for is an air pump that flows properly. With VAG-COM there are self diagnostic tests that will cycle the air pump on/off. If it makes a high pitch noise sort of like a jet engine, it may be due for replacement. The air pump typically kicks in when the car is running and idleing. It won't run constantly, usually for about 10 seconds and then shut it off. It's purpose is to pump air into the exhaust which helps improve catalysts when the cat isn't fully up to temp. I've even seen mine run even when the car is fully up to temp. YMMV.
Next on the list to check is the kombi valve(s). You can try and check for their functionality while still on the car, but this may be hit or miss. You need a hand vacuum pump to do this. Use the vacuum pump and pump it up to about -20. If you suddenly release the vacuum, and can feel/hear a nice little thunk from the valve, the diaphragm is probably fully opening and closing. If you don't hear or feel it, it could be sticking. What you want to do then is remove the kombi valve from the car. Use some brake cleaner, and spray it out with the valve both open and shut (use the hand pump). You should have a lot of carbon build up wash out. Operate it off the car and see if you can get smooth operations in the opening and closing. If you do, the valve is probably fine and you saved yourself from buying a new valve. If you are at this stage, it's best to engage in the next repair I have listed.
Carbon build up in the kombi valve exhaust passage is probably the hardest to diagnose. I have yet to see any Audi technician troubleshoot this or even attempt a guess at this could be the problem; but it was an issue on my car. I was able to track this down, but it took a little while. When my air pump ran, I could feel the idle get a little rougher. What I ended up doing was hooking only 1 kombi valve up at a time to the vacuum solenoid to see if I could figure out what side was the culprit. This worked. I was able to get a rough idle on 1 bank, and not on the other. Once I took off the kombi valve, I used a coat hanger to clean out the carbon in the air passage. I could feel a sizeable blockage near the entrance. I then used brake cleaner to clean the passage even more. Brake cleaner does a great job at disolving carbon. Use some spare vacuum hose (hard nylon line if you have it) to shove in the passage. Use the straw on the brake cleaner can, insert it in the hose, and spray away. Follow up with more coat hanger cleaning. Be careful not to break anything off or get something stuck in that passage way. If you do, you'll basically have to pull the head to try and get it out of there.
The last thing potentially that could be a problem is the solenoid for the vacuum lines. I have yet to seen these fail. The 2.8 has two of these actually. One for the kombi valves, one for the intake manifold. VAG-COM in it's self test mode will test these and you'll be able to hear them working.
So to summarize, check the vacuum hoses and replace first. Then check the air pump. Then check the kombi valves and carbon buildup.
The first and most common problem is broken/frayed vacuum lines that run to the kombi valve(s). If you have a 2.8, there was a recall on most of them to update the vacuum lines to beefier lines. If this wasn't you, or you have a 1.8, it's still easy to check the vacuum lines. If they even look suspect, just replace them. Vacuum hose is cheap enough and easy to change out. Vacuum lines don't last forever, and heat/age will wear them out.
The next thing to check for is an air pump that flows properly. With VAG-COM there are self diagnostic tests that will cycle the air pump on/off. If it makes a high pitch noise sort of like a jet engine, it may be due for replacement. The air pump typically kicks in when the car is running and idleing. It won't run constantly, usually for about 10 seconds and then shut it off. It's purpose is to pump air into the exhaust which helps improve catalysts when the cat isn't fully up to temp. I've even seen mine run even when the car is fully up to temp. YMMV.
Next on the list to check is the kombi valve(s). You can try and check for their functionality while still on the car, but this may be hit or miss. You need a hand vacuum pump to do this. Use the vacuum pump and pump it up to about -20. If you suddenly release the vacuum, and can feel/hear a nice little thunk from the valve, the diaphragm is probably fully opening and closing. If you don't hear or feel it, it could be sticking. What you want to do then is remove the kombi valve from the car. Use some brake cleaner, and spray it out with the valve both open and shut (use the hand pump). You should have a lot of carbon build up wash out. Operate it off the car and see if you can get smooth operations in the opening and closing. If you do, the valve is probably fine and you saved yourself from buying a new valve. If you are at this stage, it's best to engage in the next repair I have listed.
Carbon build up in the kombi valve exhaust passage is probably the hardest to diagnose. I have yet to see any Audi technician troubleshoot this or even attempt a guess at this could be the problem; but it was an issue on my car. I was able to track this down, but it took a little while. When my air pump ran, I could feel the idle get a little rougher. What I ended up doing was hooking only 1 kombi valve up at a time to the vacuum solenoid to see if I could figure out what side was the culprit. This worked. I was able to get a rough idle on 1 bank, and not on the other. Once I took off the kombi valve, I used a coat hanger to clean out the carbon in the air passage. I could feel a sizeable blockage near the entrance. I then used brake cleaner to clean the passage even more. Brake cleaner does a great job at disolving carbon. Use some spare vacuum hose (hard nylon line if you have it) to shove in the passage. Use the straw on the brake cleaner can, insert it in the hose, and spray away. Follow up with more coat hanger cleaning. Be careful not to break anything off or get something stuck in that passage way. If you do, you'll basically have to pull the head to try and get it out of there.
The last thing potentially that could be a problem is the solenoid for the vacuum lines. I have yet to seen these fail. The 2.8 has two of these actually. One for the kombi valves, one for the intake manifold. VAG-COM in it's self test mode will test these and you'll be able to hear them working.
So to summarize, check the vacuum hoses and replace first. Then check the air pump. Then check the kombi valves and carbon buildup.
The following 4 users liked this post by Žob:
10-25-2005, 01:58 PM
#3
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great writeup! i just had to replace one of the hoses since it broke off
it makes noise only at startup for like 10-20 secs and then a couple of minutes later another 10 sec run. i assume it's fine?
cheers,
Alen
cheers,
Alen
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08-17-2018, 05:57 AM
#9
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Cylinder Head/port clogged with carbon
Secondary air injection seems to be something sooner or later every Audi owner has a problem with. Let me run down the symptoms and then the steps to fix them. This should be the definitive guide on how to repair the system. If you had an issue & repair that wasn't covered by this guide, please shoot me an email.
The first and most common problem is broken/frayed vacuum lines that run to the kombi valve(s). If you have a 2.8, there was a recall on most of them to update the vacuum lines to beefier lines. If this wasn't you, or you have a 1.8, it's still easy to check the vacuum lines. If they even look suspect, just replace them. Vacuum hose is cheap enough and easy to change out. Vacuum lines don't last forever, and heat/age will wear them out.
The next thing to check for is an air pump that flows properly. With VAG-COM there are self diagnostic tests that will cycle the air pump on/off. If it makes a high pitch noise sort of like a jet engine, it may be due for replacement. The air pump typically kicks in when the car is running and idleing. It won't run constantly, usually for about 10 seconds and then shut it off. It's purpose is to pump air into the exhaust which helps improve catalysts when the cat isn't fully up to temp. I've even seen mine run even when the car is fully up to temp. YMMV.
Next on the list to check is the kombi valve(s). You can try and check for their functionality while still on the car, but this may be hit or miss. You need a hand vacuum pump to do this. Use the vacuum pump and pump it up to about -20. If you suddenly release the vacuum, and can feel/hear a nice little thunk from the valve, the diaphragm is probably fully opening and closing. If you don't hear or feel it, it could be sticking. What you want to do then is remove the kombi valve from the car. Use some brake cleaner, and spray it out with the valve both open and shut (use the hand pump). You should have a lot of carbon build up wash out. Operate it off the car and see if you can get smooth operations in the opening and closing. If you do, the valve is probably fine and you saved yourself from buying a new valve. If you are at this stage, it's best to engage in the next repair I have listed.
Carbon build up in the kombi valve exhaust passage is probably the hardest to diagnose. I have yet to see any Audi technician troubleshoot this or even attempt a guess at this could be the problem; but it was an issue on my car. I was able to track this down, but it took a little while. When my air pump ran, I could feel the idle get a little rougher. What I ended up doing was hooking only 1 kombi valve up at a time to the vacuum solenoid to see if I could figure out what side was the culprit. This worked. I was able to get a rough idle on 1 bank, and not on the other. Once I took off the kombi valve, I used a coat hanger to clean out the carbon in the air passage. I could feel a sizeable blockage near the entrance. I then used brake cleaner to clean the passage even more. Brake cleaner does a great job at disolving carbon. Use some spare vacuum hose (hard nylon line if you have it) to shove in the passage. Use the straw on the brake cleaner can, insert it in the hose, and spray away. Follow up with more coat hanger cleaning. Be careful not to break anything off or get something stuck in that passage way. If you do, you'll basically have to pull the head to try and get it out of there.
The last thing potentially that could be a problem is the solenoid for the vacuum lines. I have yet to seen these fail. The 2.8 has two of these actually. One for the kombi valves, one for the intake manifold. VAG-COM in it's self test mode will test these and you'll be able to hear them working.
So to summarize, check the vacuum hoses and replace first. Then check the air pump. Then check the kombi valves and carbon buildup.
The first and most common problem is broken/frayed vacuum lines that run to the kombi valve(s). If you have a 2.8, there was a recall on most of them to update the vacuum lines to beefier lines. If this wasn't you, or you have a 1.8, it's still easy to check the vacuum lines. If they even look suspect, just replace them. Vacuum hose is cheap enough and easy to change out. Vacuum lines don't last forever, and heat/age will wear them out.
The next thing to check for is an air pump that flows properly. With VAG-COM there are self diagnostic tests that will cycle the air pump on/off. If it makes a high pitch noise sort of like a jet engine, it may be due for replacement. The air pump typically kicks in when the car is running and idleing. It won't run constantly, usually for about 10 seconds and then shut it off. It's purpose is to pump air into the exhaust which helps improve catalysts when the cat isn't fully up to temp. I've even seen mine run even when the car is fully up to temp. YMMV.
Next on the list to check is the kombi valve(s). You can try and check for their functionality while still on the car, but this may be hit or miss. You need a hand vacuum pump to do this. Use the vacuum pump and pump it up to about -20. If you suddenly release the vacuum, and can feel/hear a nice little thunk from the valve, the diaphragm is probably fully opening and closing. If you don't hear or feel it, it could be sticking. What you want to do then is remove the kombi valve from the car. Use some brake cleaner, and spray it out with the valve both open and shut (use the hand pump). You should have a lot of carbon build up wash out. Operate it off the car and see if you can get smooth operations in the opening and closing. If you do, the valve is probably fine and you saved yourself from buying a new valve. If you are at this stage, it's best to engage in the next repair I have listed.
Carbon build up in the kombi valve exhaust passage is probably the hardest to diagnose. I have yet to see any Audi technician troubleshoot this or even attempt a guess at this could be the problem; but it was an issue on my car. I was able to track this down, but it took a little while. When my air pump ran, I could feel the idle get a little rougher. What I ended up doing was hooking only 1 kombi valve up at a time to the vacuum solenoid to see if I could figure out what side was the culprit. This worked. I was able to get a rough idle on 1 bank, and not on the other. Once I took off the kombi valve, I used a coat hanger to clean out the carbon in the air passage. I could feel a sizeable blockage near the entrance. I then used brake cleaner to clean the passage even more. Brake cleaner does a great job at disolving carbon. Use some spare vacuum hose (hard nylon line if you have it) to shove in the passage. Use the straw on the brake cleaner can, insert it in the hose, and spray away. Follow up with more coat hanger cleaning. Be careful not to break anything off or get something stuck in that passage way. If you do, you'll basically have to pull the head to try and get it out of there.
The last thing potentially that could be a problem is the solenoid for the vacuum lines. I have yet to seen these fail. The 2.8 has two of these actually. One for the kombi valves, one for the intake manifold. VAG-COM in it's self test mode will test these and you'll be able to hear them working.
So to summarize, check the vacuum hoses and replace first. Then check the air pump. Then check the kombi valves and carbon buildup.
My questions are:
1. Is $2800-$3500 a reasonable price? How many hours would it take?
2. Can it be done with a spray or cleaner? (like this one: CRC GDI IVDŽ Intake Valve & Turbo Cleaner)
3. On a scale of 1-10, how hard is it to do on my own? (I've never taken an engine completely open before, but I am mechanically inclined and have friends who could help)
4. Would clogged cylinder heads be a symptom of some other failure? (like a bad secondary pump, for example)
I thought it was a good deal at $2500, wasn't expecting more than $500-$1000 in repairs. Very clean looking car, single owner, no accidents. Thanks ahead of time.
08-19-2018, 02:38 AM
#10
AudiWorld Senior Member
Sounds like the shop is not an Audi indie shop, meaning one that specializes in Audi, particularly ones this age. Newer Audi with direct injection has this issue. Not ones of this vintage. Doesn’t mean you couldn’t have carbon build up as described in this thread, but not one that should come close to that extensive. I would continue to do research like you did to find this excellent old post. After you have read several you will get a feel for common failures of this nature and will be able to choos e a course of action. Chances are your issue can be cleaned up yourself with some new hoses and some cleaning as described.
I would not put more than a few hundred at most for this problem. Likely you can DIY for under $200. It is a good car to drive if maintained but not one I would take to a shop. My son has this same car. Got it 6 years ago as a 16 year old and we have not done much of anything to it other than the normal brakes, oil changes, timing belt services, CV boots. Just a solid daily driver.
I would not put more than a few hundred at most for this problem. Likely you can DIY for under $200. It is a good car to drive if maintained but not one I would take to a shop. My son has this same car. Got it 6 years ago as a 16 year old and we have not done much of anything to it other than the normal brakes, oil changes, timing belt services, CV boots. Just a solid daily driver.