wtmmm

It's me again... I have an '05 A6 3.2 and have been experiencing the surging at low loads (typically attributed to a bad Torque Converter). The car accelerates smoothly and idle is sometimes fine, sometimes a bit rough. This has been going on for a year now and it comes and goes in severity; sometimes worse when car is cold and cold outside. (see below the repair items). The car has been showing a cylinder #4 misfire.

Also about 6 months ago my car has started to stall in certain circumstances, usually when restarting it while it is warm. It appears like it will turn over but when I release the key, it just stalls, as if it is out of gas. After it sits for 20 min, it will finally turn over and start without stalling.

I believe that these are two different issues but they could be related and a result of something with FSI. The only idea we have now is to swap out the #4 injector/coil pack/plug with other ones.

My question.... is there a way to scan the car with VCDS to clearly identify what is causing these two problems? Has anyone been able to identify the bad TC with a scan?

Ross-Tech has given me different scans to perform but nothing is showing up. (Engine 005, 031, 140, 103, 106 and Trans 001, 002, 003.) Also tried to do basic settings 103 and 107 but they do not seem to run the tests properly. I log the car while driving and hit the marker when it surges but apparently nothing looks strange on the logs.

Here are the repairs that have been done to date (most recent items first):

Fuel additive
Fuel Filter
Air filter
Spark plug #4
Replaced Auto Transmission Fluid
Auto Trans Filter
Cam position Sensor
Mechanical Fuel Pump
Electric Fuel Pump Assembly (in gas tank)
Cleaned and Adapted throttle body again (third time)
Cyl #4 Ignition Coil
Audi Dealer performed a intake valve cleaning service ($1,300)
Audi Dealer cleaned and adapted throttle body (second time)
Fuel additive
Replaced Low side Fuel Pressure Regulator
Cleaned Throttle Body (first time)

newa6er

Vacuum leak can cause surging, and this car in known to have vacuum leaks

You could have a bad sensor, the bad MAF would fit your problems

these are just guesses

if you swap the injector and coil pack and plug from #4 to another and #4 still has problems, run a leak down test on #4

wtmmm

My car is with a local VW dealer. They have diagnosed the surging and stalling to be a result of a bad throttle body and not the torque converter. They quoted $1,700 for the new throttle body, some related sensors/hoses and labor. They are confident that this will resolve all surging issues.

Question for everyone here, do you think that it could be the TB and not the TC?

I would be happy to pay this to replace the TB if it is going to resolve these two issues once and for all (this has been going on over a year and has gotten worse recently). The VW Dealer is confident that it is the TB but I doubt they will be giving me a money back guarantee. Thoughts??


I should add... recently I paid Ross-Tech $35 for them to work with me using their scan tool to diagnose the problem. After a week of talking with them and running different scans, we never determined if the problem was with the fuel delivery system or the transmission.

raj99

Hi wtmmm, have you swapped the coil packs and absolutely ensured that the spark plugs are good and in there properly? I've seen all kinds of things, so always recheck the basics before you go too deep.

Furthermore have you verified there are no vacuum leaks? A simple smoke test could really assist with this.

Also, before replacing the TB with a new one, how about cleaning the existing TB? It's relatively straight-forward and any decent indy shop will be able to clean it for you for perhaps a couple of hours of labor. Get it done BEFORE you go with a replacement.

wtmmm

Hi Raj, the VW shop just replace the N80 purge valve because they found a vacuum leak there. No other vacuum leaks spotted by them (not sure if they did a smoke test).

TB has been cleaned three times over the past year and it never resolves the surging issue. Plus the dealer is saying that the problem is not with the butterfly flaps of the TB but with the electronics of the TB which is not something they say cleaning will fix.

The coil pack and the spark plug on #4 cyl (which has thrown codes) have been replaced.

raj99

sorry, but i'm not an expert on TB electronics The dealer could be right, but try to get some sort of assurance from them that this will definitively resolve the issue.

I can understand if the engine control module is bad, but a cheaper option for you might be to get a 2nd hand one of reman unit and attempt to see if that resolves the issue.

KevinGary

I would bet that the surging issue is the very common torque converter issue that plagues our cars. Since the OP has the first year FSI engine I would think that he should consider getting a manual carbon cleaning since that seems to be a very common problem on those engines.

wtmmm

Thanks KevinGary,

The first Audi dealer did carbon cleaning last yr but that didn't fix it. (See repair list below)

I have read a lot about TC but can't understand exactly how that is diagnosed. How did they determine with your car? I have not seen any transmission codes on mine.

Current VW dealer really thinks it is TB. He has seen same problem w/ VWs frequently. Also he can hear the TB struggling at idle. He doesn't think it is with the mechanical part but rather the electronic components in the TB. Might make sense since the cleaning have never resolved the issue. He also does not think it is a bad TC because no codes, and the problem happens at different speeds and in all gears.

I really want to fix this and keep the car a few more years but I'm nervous since first Audi DLR was convinced it was carbon build up and indi shop was convinced it was fuel pumps but neither resolved issue. Finally, I just don't understand how a bad TC is diagnosed.

Here is list of things done so far (most recent first):

Purge Valve
BG44k
Ross Tech diagnosis
Fuel Filter
Air filter
Spark plug #4
Auto Transmission Fluid
Auto Trans Filter
Cam position Sensor
Electric Fuel Pump Assembly (in gas tank)
Mechanical Fuel Pump*
Cleaned and Adapted throttle body again (third time)
Cyl #4 Ignition Coil
Audi Dealer performed a intake valve cleaning service ($1,300)
Audi Dealer cleaned and adapted throttle body (second time)
Replaced Low side Fuel Pressure Regulator
Cleaned Throttle Body (first time)

KevinGary

I did not have any codes with the TC. I had surging RPMs in the 1700 to 2000 rpm range. They replaced the TC and the surging stopped. It is a very common problem and solution.

raj99

Unless the dealer is willing to give you a money back guarantee that a new tb will fix the issues, listen to Kevin. It's sounds like he's had exactly the same issue you described, which the tq fixed