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Old 10-01-2013, 11:37 AM   #1
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Default '05 A6 - Frustrating surge at low rpm, low load

Here is a long post, so be warned! Any suggestions would be appreciated...

I am still experiencing a very annoying power surge on my '05 A6 Quattro 3.2FSI with 140k mi. This has been happening off and on for most of this year. I have taken it to a local shop and to an Audi dealer 75 miles away. Both have been able to get the problem to stop temporarily but neither has been able to entirely fix the situation.

I have described this in another post but here is a recap: The problem is best described as a power surge at low rpm and low load. Typically this happens when driving at a constant speed on a flat or downhill road. It seems worse when the car is cold but it happens after it is warmed up too. The tachometer even visibly shakes. The surging stops when the car is accelerating, only to return at lower rpm.

Other threads suggested this might be a torque converter (TC) problem. I took it to my local independent shop who didn't think that the TC was really the problem (can't recall why).

He first replaced the plugs and then replaced the Fuel Pressure Regulator (low side), cleaned the throttle body and oil separator. The problem went away but slowly came back a month later.

Then I took it to the Audi dealer who didn't think the TC was the problem either. They diagnosed it as "carbon buildup" on the valves and told me a valve cleaning job should solve the problem. I paid them $1,300 to clean the valves and the car seemed to be fine, even better than before... no more surging at low rpm and/or low load.

Soon after, I got an entirely different problem. When I was in S-mode and well above 4,000 rpm, the car started to misfire badly. This is documented in a mis-named thread (sorry) called "Transmission problem '05 A6."

At the suggestion from several members, I purchased a Vag-Com scanner which gave me 2 error codes: Low Pressure Fuel Sensor and Cyl 4 Misfire. I replaced the #4 coil pack, cleared the codes and thought the problem was fixed for about a day.

Then when I got the car up to 4,000 rpm again, the misfire came back along with the same two codes. I cleared the codes and the car drove fine until it hit 4,000 rpm and - you guessed it! - it started to misfire again. Finally, after clearing the codes 3-4 times the misfiring went away completely and has not come back yet.

However, the initial surging problem is back and now the Vag-Com just gives a code of intermittent misfire on cyl 4 (no more error code: low pressure fuel sensor).

- I use only high octane fuel
- the oil/filter have been changed regularly
- the plugs are only 8 months old
- the low fuel pressure regulator was replaced
- the valves have been cleaned
- coil pack replaced

At this point, the only other idea is to swap the fuel injector in cylinder 4 with another one to see if that migrates the error code to another cylinder. That's not a job for me to do so I'll be taking it to a local shop.

Another suggestion was to replace the fuel filter, which might be a good thing to do so I'll have the shop do that too. However, I can't see where that would fix the surging since the error is constantly only in cyl 4.

Someone else suggested that the computer may need to be updated. That sounds like a dealer activity.

Again, if you have any advice it would be appreciated. The amount of time, money and energy is beginning to make me think about replacing this, otherwise, great car.
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Old 10-01-2013, 01:01 PM   #2
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read the post that I posted " first six months review" I have the shake and rough idling it's sitting at dealership now for carbon build up cleaning and valves and fuel injector on cylinder 3......but u mentioned something about S mode mine was driving fine even with the shake problem but 4 days ago I was playing " carefully" not "recklessly" with a guy who had a s5 on the road so put on sport mode more than one that day......next day morning shake was very bad and engine light came on
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Old 10-01-2013, 05:21 PM   #3
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The surging is most likely the torque converter. I had the same problem in my 2006 and that was the diagnosis. I never had it fixed, I traded it for a 2008. My recommendation is to change the fluid and filter for the tranny. If that does not work then you need a new TC.

Let us know what you find.
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Old 10-01-2013, 06:46 PM   #4
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Quote:
Originally Posted by SchwarzS6 View Post
The surging is most likely the torque converter. I had the same problem in my 2006 and that was the diagnosis. I never had it fixed, I traded it for a 2008. My recommendation is to change the fluid and filter for the tranny. If that does not work then you need a new TC.

Let us know what you find.
Thanks SchwarzS6, I just re-read your original thread - all 108 posts! I agree with you, it does sound like my car may have the same Torque Converter problem.

I don't exactly understand how the TC works and I really don't want to spend +$3k to fix it either. Especially after spending $1.3k at the Audi dealer who told me their valve cleaning to remove the carbon buildup would fix my problem.

I am curious if anyone else was able to fix the problem by simply changing the tranny fluid and the filter.
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Old 10-01-2013, 06:57 PM   #5
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when I go to pick up my car at dealership in 2 days I will ask "tim" the mechanic about your case he knows Audi very well and let you know what he says......I doing carbon cleaning now and valves
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Old 10-01-2013, 07:01 PM   #6
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Quote:
Originally Posted by chrisone View Post
when I go to pick up my car at dealership in 2 days I will ask "tim" the mechanic about your case he knows Audi very well and let you know what he says......I doing carbon cleaning now and valves
Thanks. I am interested to hear what he has to say.
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Old 10-03-2013, 04:42 AM   #7
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Quote:
Originally Posted by SchwarzS6 View Post
The surging is most likely the torque converter. I had the same problem in my 2006 and that was the diagnosis. I never had it fixed, I traded it for a 2008. My recommendation is to change the fluid and filter for the tranny. If that does not work then you need a new TC.
Can anyone comment on changing the transmission fluid and filter as SchwartzS6 suggested? Has that ever been able to fix the surging issue at low rpm?

Chrisone, please let me know if your mechanic has any comments on this. Hope they were able to resolve your issues too!
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Old 10-04-2013, 12:14 AM   #8
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I know your frustration. I had a 2005 A4 that surged at low speeds when cold, and the Audi dealesrhip in Rochester,NY, changed the fuel pump, along with the cam shaft thinkingt hat was teh problem, also told me to use higher octane. NOthing they did helped. I now own a '08 A4, and it is doingt he same thing. Noo ne seemst o know the exact remedy. Love the car, hate the surge. WOuld love yo know hoe to getit fixed. Anyone with answers is appreciated.


Quote:
Originally Posted by wtmmm View Post
Here is a long post, so be warned! Any suggestions would be appreciated...

I am still experiencing a very annoying power surge on my '05 A6 Quattro 3.2FSI with 140k mi. This has been happening off and on for most of this year. I have taken it to a local shop and to an Audi dealer 75 miles away. Both have been able to get the problem to stop temporarily but neither has been able to entirely fix the situation.

I have described this in another post but here is a recap: The problem is best described as a power surge at low rpm and low load. Typically this happens when driving at a constant speed on a flat or downhill road. It seems worse when the car is cold but it happens after it is warmed up too. The tachometer even visibly shakes. The surging stops when the car is accelerating, only to return at lower rpm.

Other threads suggested this might be a torque converter (TC) problem. I took it to my local independent shop who didn't think that the TC was really the problem (can't recall why).

He first replaced the plugs and then replaced the Fuel Pressure Regulator (low side), cleaned the throttle body and oil separator. The problem went away but slowly came back a month later.

Then I took it to the Audi dealer who didn't think the TC was the problem either. They diagnosed it as "carbon buildup" on the valves and told me a valve cleaning job should solve the problem. I paid them $1,300 to clean the valves and the car seemed to be fine, even better than before... no more surging at low rpm and/or low load.

Soon after, I got an entirely different problem. When I was in S-mode and well above 4,000 rpm, the car started to misfire badly. This is documented in a mis-named thread (sorry) called "Transmission problem '05 A6."

At the suggestion from several members, I purchased a Vag-Com scanner which gave me 2 error codes: Low Pressure Fuel Sensor and Cyl 4 Misfire. I replaced the #4 coil pack, cleared the codes and thought the problem was fixed for about a day.

Then when I got the car up to 4,000 rpm again, the misfire came back along with the same two codes. I cleared the codes and the car drove fine until it hit 4,000 rpm and - you guessed it! - it started to misfire again. Finally, after clearing the codes 3-4 times the misfiring went away completely and has not come back yet.

However, the initial surging problem is back and now the Vag-Com just gives a code of intermittent misfire on cyl 4 (no more error code: low pressure fuel sensor).

- I use only high octane fuel
- the oil/filter have been changed regularly
- the plugs are only 8 months old
- the low fuel pressure regulator was replaced
- the valves have been cleaned
- coil pack replaced

At this point, the only other idea is to swap the fuel injector in cylinder 4 with another one to see if that migrates the error code to another cylinder. That's not a job for me to do so I'll be taking it to a local shop.

Another suggestion was to replace the fuel filter, which might be a good thing to do so I'll have the shop do that too. However, I can't see where that would fix the surging since the error is constantly only in cyl 4.

Someone else suggested that the computer may need to be updated. That sounds like a dealer activity.

Again, if you have any advice it would be appreciated. The amount of time, money and energy is beginning to make me think about replacing this, otherwise, great car.
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Old 10-04-2013, 04:31 AM   #9
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I have spent hours and hours reading other posts on this subject. Everyone points to the Torque Converter. However, has anyone actually ever fixed the problem by replacing/repairing the TC?

The most common fix to the problem is to sell the car. I don't want to do that since it is in great shape and otherwise a good car. Only 140k miles doesn't seem like enough miles to have to dump the car.
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Old 10-04-2013, 08:09 AM   #10
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spoke to mechanic about your car and told him exactly what you wrote down and he says it's very difficult to say exactly what's wrong with car unless he sees it " typical " mechanic words but he said it's 50% possibility that you TC needs to be changed at 140k .....but also he said it could be a fuel system problem as well.....best thing is have two different mechanics "Audi expert" and see what they say and match it with what you feel
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Old 10-04-2013, 08:09 AM
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