LarryJa

Recently, I did another can of Gumout "Regane" to clean the valves & the throttle body a little, again. I'm trying to do this about every 10k miles to keep the carbon build up at bay.
However, I still notice a little light throttle surging, especially when the engine is cold. But, VCDS is not giving me any codes.
I'm thinking the throttle body could use a little more cleaning, or O2 sensor(heaters) are getting weak. Maybe, other sensors, or old spark plugs?
Any experience here?

SchwarzS6

Search the forum. There are numerous threads about this. The problem is related to the transmission. AFAIK all of these cars do it to some extent but if the torque converter goes bad they will do it all of the time. If it goes away when it warms up, don't worry about it.

uberwgn

Yeah, Larry, others have said it's related to the torque converter. Our car does it when the engine is cold, it's very slight. I think it's more noticeable when ambient temps are cold and the car is cold.

LarryJa

I guess I'll add another trans fluid (LG6+, blue) change to my "2017 summer maintenance" list. I'll do a drain & refill (5L) to see if the freshened fluid will help this. Previously, I did two fluid changes, as part initial maintenance, owning this car.
It's curious that this surging only became noticeable to me recently. My car has 175k miles on it & I've owned it a year & driven it the last 25k miles.
We'll see....

KevinGary

The torque converter is the likely culprit.

SchwarzS6

Also, I think that once you notice it you are sensitized and are more likely to look at the tach at the right moment. Before you saw it the first time you were ignorant to the problem.

LarryJa

Actually, what I recently became aware of is the slight hesitation/flat spot at low (50-60mph) highway speeds. That just got my notice recently. Then, I started to notice the slight surging. The cold running surging has been around this past spring, in particular, though.

Ryanjayx

If you messed with the throttle-body, did you reset it using VAGCOM? When it hesitates, does the EPC light come on for just a quick second?

LarryJa

Using the Gum out "Regane", I just sprayed it into the intake with the engine running at about 1500-2000rpm. So, I've done no disassembly or anything mechanical to the throttle body.
I've run VCDS scans on the engine & have no codes up. So, I haven't run the throttle alignment/adaptation routine. I'll have to give that a shot!
BTW: I've just seen that Seafoam makes an "intake/upper engine spray" cleaner that looks like it'd do a better job than the Gumout stuff. It has a small tube that slips into the air intake track, in between the air intake tube & the throttle body, & you spray it in with the engine at fast idle. In the future, I'll give it a try

wtmmm

The throttle body may be the problem. I had surging on an A6 and also thought it was torque converter or something with the fuel system from other posts but the TB was cracked (not visible). When it was replaced the surging went away.