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Turbo Flutter and slight delay-After New Stock Turbo

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Old 06-27-2017, 08:48 PM
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Default Turbo Flutter and slight delay-After New Stock Turbo

I just purchased a 2000 Audi TT 1.8 manual transmission coupe. The car has 150K miles

When I purchased the car it had 147K miles. I did get the service records and noticed that some of the major work wasn't done. So before extensively driving it around I had the following work done:

Timing Belt kit from ECS Tuning-
Timing Belt
Tensioner Roller
Tensioner Assembly
Idler Roller
Water Pump With Metal Impeller
Accessory Drive Belt
Thermostat
Thermostat Housing
Engine Mount Bolt Kit (7pcs)
Camshaft Seal
Crankshaft Seal
Crankshaft Gear Bolt

Fuel Filter
Cabin Filter
Dog Bone Mount
Air Filter
Akebono brake Pads
Meyle Rotors
NGK spark plugs
Mob 1 oil
Mob 1 oil filter
ABS wiring harness (abs light wouldn't go away)
used ABS module (old one had a bad pump-light finally went off)


When all of this was done. I drove the car about a week and noticed that the car had a metallicy flutter noise and loss of power. It drove like a used 4 cycl vehicle. I think a few times even an old Sentra passed me by coming out of a red light. I was like WTF. Something has to be wrong. So I googled searched..and read and read and decided to change out some more parts. Next round of work that was done:

new Borg Warner Turbo (same as the stock)
PCV valve (smaller black/grey valve)-genuine audi
Turbo Boost Control Valve-genuine audi
BOV valve-genuine audi
tranmission mount
flex disc
LUK clutch kit-throwout/slave, plate, &clutch disc (i hate this pressure plate though, because when i step on the clutch pedal, its softer than before)


Power!!! The car is zippy again. HOWEVER, after driving it around for a week, the fluttery sound came back when I take the foot off the gas, regardless of whether i depress the clutch pedal or not. It doesn't have the metallic sound like it did before the turbo change, but still fluttery...like pigeons or like when a horse does that air sound from its nostrils. And it also seems as if there is at times a very slight delay in boost (i might be imagining this). It also seems RPM dependent. The higher the RPM, the softer the flutter sound or no flutter at all (and that's based on stepping on the gas and rev-ign up the car-tachometer is broken so I don't know the RPMs). It is driving much better than before...

I haven't driven the car much and don't have experience with a turbocharged car, but I just don't feel that the flutter every time I let off the gas, is normal.

What else should I check? I've invested now a lot on this car and would definitely like to keep going since it's almost done to stock. Is there something else I missed? Throttle or MAF maybe?

Thank you
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Old 06-28-2017, 08:44 AM
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Sounds like what my son's did which was a combination of the diverter valve (fixed most of it) and a broken elbow in a vacuum line (fixed the minor issue after). Others?
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Old 06-28-2017, 07:42 PM
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Thank you Lyleswk. So you believe it could be a vacuum line? While I was driving home from work today, I did notice that at times there is no flutter noise..the car jams and runs great. It almost feels like its effortlessly gliding (and feels so fun to drive). But then for no reason all of a sudden, I'll get the flutter sound when I take my foot off the pedal during differant traffic conditions and having to increase/decrease speed. Sometimes a slight flutter, then other times a bit louder.

With the turbo, I purchased an install kit that had a bunch of seals and gaskets. I asked the mechanic to check everything that he was swapping from the old turbo to the new turbo to make sure there wasn't any cracks in the hoses. He said there wasn't any.

Do you know what vacuum line to go take a look at? I can't afford to keep paying the mechanic, so I"ll have to go take a look myself. If you can guide me in the general area I can probably tackle it myself.

Thank you!
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Old 06-30-2017, 08:09 PM
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I will check for vacuum leaks this weekend and report back if I find anything.
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Old 07-05-2017, 08:01 AM
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Sorry, been away for a while. On my son's, it was one of the lines that goes the DV. If you follow the line that runs back by the firewall over to the passenger side, it makes a 90 degree turn right at the firewall. The 90 fitting was cracked. I found it by wiggling lines with the engine running and heard a faint hiss. Of course it could be anywhere only the run.
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Old 07-05-2017, 10:47 AM
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Originally Posted by lyleswk View Post
Sorry, been away for a while. On my son's, it was one of the lines that goes the DV. If you follow the line that runs back by the firewall over to the passenger side, it makes a 90 degree turn right at the firewall. The 90 fitting was cracked. I found it by wiggling lines with the engine running and heard a faint hiss. Of course it could be anywhere only the run.
I will check. I'm also putting together a smoker, so hopefully I find any leaks with that.

​​​​​​​I appreciate the reply.
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Old 07-05-2017, 11:24 AM
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Suggest you pressure test the intake system. This is the best way to find a boost-- vacuum leak. Set the regulator no higher than 15 psi. Listen. You'll hear them. The most common are under the intake manifold.
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Old 07-05-2017, 10:03 PM
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Great! Thank you J. Patterson. I'll also test the intake. Hopefully this will lead to what is causing the fluttering.
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Old 07-16-2017, 10:51 PM
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Any updates? Sounds just like a vacuum leak or a diverter valve fluttering. If it only when coming off boost or does it happen with foot into it to the floor?
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Old 07-16-2017, 11:14 PM
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No, no updates. It's been really hot here in N. Cali and I've had a hard time finding some help in this heat. I did make a paint can smoker, so it shouldn't be too hard to do, right? I have a new diverter valve installed. What are the chances that the new one installed was bad?

It only happens when I let off the gas pedal. Interesting...I also noticed that in the afternoon when its been scorching hot, it doesn't do it as much and the car runs really really well. Seems like a vacuum leak to me since it runs better when the air is hot.

I also have not ever had any CEL. so makes things a bit more frustrating.

This coming weekend I will roll up my sleeves even if I don't get any help to check for vacuum leaks. I will report back any findings.

Thank you so much for your response. I appreciate all the help I can get.

Carol
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