Surging under boost - did some searching - am I missing anything?

[96tdiwagon]

So since I got my car, it has experienced some surging under boost.

The problem was made 'worse' (or simply amplified) when i bought my .216 injectors and then again when I installed my TDTuning Stage 2 tune.

I did some searching and found that a common culprit can be the fuel filter and the N75. My fuel filter looks ancient and i have a couple other small issues that make me think its time for repair, so i have ordered one. As well, i am about to order an N75 valve to go with it (on a side note - what other TDI's have this same N75?).

I've replaced all my vaccuum and boost lines, my air filter looks clean, the car has no cat... all of these i have read could also effect it.

I dont have a vagcom personally but a friend of mine does and i could take a look at some logging if need be - i'll be doing the fuel filter regardless and probably the N75.

Thanks guys

- Phil

 

[mohawk69]

"I've replaced all my vaccuum and boost lines"

Does that include the one INSIDE the ECU?

 

[96tdiwagon]

I inspected it and it seemed to be fine, although starting to get a tad soft. I can replace that pretty easily if its worth a shot but it seemed to be overall in good shape

 

[kooyajerms]

Just do it, sometimes you can't see the leak.

 

[greenskeeper]

what speed/rpm/gear are you getting the surge?

 

[96tdiwagon]

It's pretty much only under boost, so i dunno, 2500rpm and over on full throttle/boost.

 

[Seatman]

I had that sort of thing happen on my last car with the AGR, it's basically the ALH but with the wastegate turbo. Anyway I took the thing apart and cleaned the turbo, intake and egr and after that everything ran great. I'd check the wastegate isn't sticking a little bit as they do get sooted up and can get sticky, mine was.

 

[96tdiwagon]

Is there anyway to unstick the wastegate? That is another thing i wanted to check as well...

 

[Seatman]

Must be able to do it using the actuator or a big screwdriver, I had the turbo off anyway so it was easy but I'm sure it can be done in situ.

 

[rdkern]

I've read that powerblaster and either the screwdriver or pump (to force the wastegate open) repeatedly helps. If it was driven softly, the wastegate can crud up.

 

[96tdiwagon]

I'll have to give this a try. I noticed today that the car doesn't do this under near full throttle, only when the pedal is to the floor.

 

[BKmetz]

I had this problem a few years ago. It was a combination of bad vacuum/boost lines and a failing N75. That eliminated 90% of the surge. So what cured the last 10? A new MAF sensor. All the A3/B4s are old enough now to have weak MAF sensors regardless of mileage so don't ignore it.

 

[slapshotjh]

Check to see that the little lines from the N75 aren't clogged with goo. I chased a limp and surge problem for months. I had the lines on the car spec'd on this site from Mcmaster carr for a couple of years. One day I took off both ends of the blue line and tried to blow through it. It was plugged with black goo. Cleaned out the goo (and since replaced the line again) and no problems.

 

[keks]

Check to see that the little lines from the N75 aren't clogged with goo. I chased a limp and surge problem for months. I had the lines on the car spec'd on this site from Mcmaster carr for a couple of years. One day I took off both ends of the blue line and tried to blow through it. It was plugged with black goo. Cleaned out the goo (and since replaced the line again) and no problems.

Was your problem surging under boost also? My car started doing the same thing. Around around 25k she starts pulling then stopping, pulling then stopping.. It almost feels like im riding on a swing sorta all the way to red line.