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Discussion Starter #1
Hello all, if any formatting is incorrect, I apologise as I am on mobile.

Anyways, I have a golf TDI I bought cpo from a dealer I work for. It's in like new condition and I got it cheap. Currently at about 90k miles and running strong except the fuel economy is terrible. It gets 20mpg and worse at times. I drive around 350 miles per week, and I am putting in about 12 gallons or more per fill up, whereas before I was putting in 6-7. The power is also shit as well, this this g used to fly off the line but now it only has power when I floor it.

I am a technician so any advice that's on the technical side of things is welcome. One problem I also noticed is that the brake pedal sometimes goes rock hard as if there's no assist, the back to normal a second later. Weird, but since the vacuum is provided from the vacuum pump I am not concerned as I know there's a small line that cracks on the booster side that causes this. However, I smoke tested the system and after that, the gas mileage was great for 2 days, then it was back to crap and the power was still bad. I've noticed currently that it's eating about 3/4 a tank per 350 miles which is trash. I really need help with this one as I and the other techs can't find anything wrong. Any advice is appreciated, thanks!
 

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First posts normally go in introductions else you could get a free fix and we never see you again!!!

Forum Rules and Guidelines

Any problems search TDI Wiki as that covers write ups and forum posts.

You need to get your motor scanned (preferably with VAG-COM\VCDS) for any error codes logged in the ecu and post them, that will save a lot of guessing and check systems out.

Manufacturer: VW, Date(s) Used: 05/2011-05/2013, Model: Golf GT, Engine Code: CJAA, 103Kw, 140PS, 2.0 Ltr, 4 Cyls, Remarks: North American Region (NAR): Turbocharged Direct Injection Common Rail (TDI-CR) Timing belt
 

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Discussion Starter #3
First posts normally go in introductions else you could get a free fix and we never see you again!!!

Forum Rules and Guidelines

Any problems search TDI Wiki as that covers write ups and forum posts.

You need to get your motor scanned (preferably with VAG-COM\VCDS) for any error codes logged in the ecu and post them, that will save a lot of guessing and check systems out.

Manufacturer: VW, Date(s) Used: 05/2011-05/2013, Model: Golf GT, Engine Code: CJAA, 103Kw, 140PS, 2.0 Ltr, 4 Cyls, Remarks: North American Region (NAR): Turbocharged Direct Injection Common Rail (TDI-CR) Timing belt
Sorry about the first post rule,d see that when I glanced over them.

Also, I work for a VW dealer so i used the factory scan tool, no codes.
 

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Discussion Starter #5
If you work for a VW dealer you must have talked to the tech guys about your problem. So what do they suggest?
Alrighty, I'm off of work now and have a moment to make a more detailed reply, so here it goes. My background is at a Mazda/Volkswagen dealership, however I travel a lot for work. I specialize in Mazda vehicles and dabble with VW, however the technical concepts are the same so I understand it from a textbook standpoint.

So, I have used the factory scan tool (ODIS) and done the following: DPF regen, checked differential pressures on each side of the DPF, under 300mmhg so inside of specification for a CJAA engine. I also checked to see if the thermostat was stuck open as we've seen that a lot which causes the car never to pass inspection (TDI only problem).
So other than that, it's either the turbo or some other random small component. Haven't gotten to sensor testing yet, but here's something odd: I leak tested my intake as I was thinking maybe a small leak causing this. Nope. So I went and I drove it home and, holy shit, my gas mileage is great? 2 days and I had great mileage, after that it immediately went back to shit, why????

I'm really stuck here, and I'm thinking the better mileage was just a coincidence but I may try it again and see what happens.
 

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Has it had the VW dieselgate "fix" done to the programming? That puts a sizable dent in the power and mpg. 12 gallons for 350 miles if that is mostly city driving sounds about right for a dieselgate car with the fix. Mixed driving mine averaged about 34 mpg before the fix and 29 after.
 

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Discussion Starter #7
Has it had the VW dieselgate "fix" done to the programming? That puts a sizable dent in the power and mpg. 12 gallons for 350 miles if that is mostly city driving sounds about right for a dieselgate car with the fix. Mixed driving mine averaged about 34 mpg before the fix and 29 after.
This is solidly highway driving, but don't worry we found the issue, I have one hell of an update for this thread.

Before I start, I would like to point out that malone makes a tune stage 0.5 that is for people who don't want to upgrade DSG software, this gives you your fuel mileage and power back from before the update and requires no modification whatsoever.

Now, onto my situation. Well, the other day while at a stop sign, my car went suddenly into limp-home mode. I put the trans in manual mode and got back to work just fine. Got the ODIS out and had 2 codes for supercharger/turbocharger underboost and boost position sensor A circuit. There is a TSB for these two codes that led us to test the wastegate actuator and it's fucked. Ordered parts, warranty is paying for everything. Got home yesterday and DPF light comes on, I scanned it with an Autel MaxiCom MK808 and would you look at that, DPF regen required. Well that's funny, I regen'd it last month. Checked differential pressures while driving (again) and would you look at that, specification is for the pressure difference to be no more than 300 inhg, it's 418 right now. Regen again and the light goes off, pressure difference stays the same and now there's p244B in the system, differential pressure too high. Since I'm a Mazda tech and know nothing about these diesels, I asked a coworker who is a VW tech and he said that DPF is likely going to have to be done as well, plus he's worried about the condition of the turbocharger if the wastegate was stuck open for too long as it might no longer seal properly. We're going to do a full diagnostic session on Monday and I'll update with the results.
 
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