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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW B5 Passat TDIs

VW B5 Passat TDIs This is a general discussion about B5 Passat(>98 (2004-2005 in North America)). Non TDI related postings will be moved or removed.

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Old July 29th, 2019, 23:19   #106
Gnant
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Join Date: Jul 2019
Location: Scottsdale AZ
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Sorry to bring the infamous P0299 code back to the top. But after much reading, and much work, I can't seem to get this code cleared up. It is a 2005 Passat 2.0 TDI with 110,00 miles. Immaculate shape so it is well work getting road worth.

What has been done so far.

1) new turbo and N75 valve done at a shop as they said that is what it was. Code was still present.

Car then sat for two years out of frustration. In the last 10 days I have done the following.

2) all new vacuum lines and routing is confirmed as correct. All held vacuum including the reservoir.
3) new vacuum pump as it was leaking at the port to the check valve for the brakes.
4) vacuum tested the N75 and it was operating smoothly
5) removed all inter-cooler hoses and inspected. All solid shape.
6) replaced EGR as it had clearly been stuck for a while and the motor was burned out.
7) inspected butterfly valve next to EGR and was clean.
8) installed new waste gate solenoid as it was leaking.
9) pulled top and bottom metal hoses for the turbo and replaced metal gaskets. Hoses were fine.
10) for giggles put in a new boost sensor. That was a waste.
11) confirmed clean airbox and new filter.
12) replaced fuel filter and now have 13 PSI

The car has way more power and the code now appears as a soft code usually unless I stand on it. The thing is I have turbo for about a minute, no matter how I drive it then the computer is kicking it off. I can clear the code while driving and she scoots, but for a minute. I can also turn on and off the key (yes while going down the road), and again, turbo works great, but for a minute.

I would like to Ohm test the MAF sensor but can't seem to find specs if anyone could help me out. I am also highly suspicious of the gas pedal because if I floor it softly, I don't get the turbo response I do if I stomp on it quickly. I mean smash it.

Related to the gas pedal, what I would like to confirm is that my throttle position sensor reading is stuck on 95.3. From my reading that is the butterfly valve next to the turbo and it is supposed to be full open and only closes when the car is shut off to stop the engine from a run-on condition. Do I have that understanding correct?

Also, is there way to test the inter-cooler beyond a smoke test? Any help is appreciated. This place has been very helpful and I have read as much as I could but I am stuck at this point.
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Old July 30th, 2019, 21:05   #107
Scubanero
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I have had O-ring leaks that were not apparent from visual inspection or while the engine was running. I made a cap for the turbo inlet and a fitting to go over the hose end that clips into the anti-shudder valve. The latter had an air hose fitting. I set my air regulator to 10 psi and kept air flowing until I could hear and feel where it was coming out.
You are correct on the butterfly (anti-shudder) valve operation. I believe the TPS is actually a pedal position sensor.
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Old August 1st, 2019, 08:48   #108
Gnant
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Quote:
Originally Posted by Scubanero View Post
I have had O-ring leaks that were not apparent from visual inspection or while the engine was running. I made a cap for the turbo inlet and a fitting to go over the hose end that clips into the anti-shudder valve. The latter had an air hose fitting. I set my air regulator to 10 psi and kept air flowing until I could hear and feel where it was coming out.
You are correct on the butterfly (anti-shudder) valve operation. I believe the TPS is actually a pedal position sensor.
For the price of O-Rings, I think the thing to do is just replace them. Thanks for the suggestion as they all did look good visually. I like your suggestion for testing the inter-cooler itself. So if the O-rings aren't it, I will make a similar setup.
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Old August 6th, 2019, 09:13   #109
N2OKX
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Join Date: May 2005
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Default 9 hours later on P0299 turbo underboost

I was working a 2005 Passat TDI with 246,000 miles. Presented with the infamous P0299 code plus P0741 (torque converter!). Since the owner admitted he had run off the road (front grill inserts missing), I started with the turbo hoses/ducting, but only a visual inspection. Later, I did a pressurized smoke test. All okay.
Of course, I checked the movement of the turbo wastegate actuator rod by pulling vacuum and measured the vacuum near the tandem pump. Again, all good.
Finally, I pulled the N75, Wastegate bypass regulator valve and checked it. It was not holding a perfect vacuum, so I replaced the valve, thinking that I finally isolated the problem. In retrospect, the problem was the opposite of what the DTC indicated. I should have been looking for a vacuum leak.
During all this, I reviewed most of the posts in this extensive thread. By the way, very few solutions were posted. Folks, please follow-up with what fixed the car. Maybe that is hard to do for this code, since there are multiple causes and they are very hard to find with absolute certainty.
I thought I had already checked all the vacuum hoses, but this morning after concluding there had to be a vacuum leak, I finally got breakthrough! I ended up pulling a vacuum on each section of hose until I found the culprit. It was the hose from the "out" nipple to the turbo. At first I suspected the rubber el, but after pulling it off and checking just the hose, I found that the hose did not hold vacuum. The hose looked perfectly okay. It was only after very close inspection that I found a slit near where the hose connects to the rubber el. On a Passat, this N75 valve is buried deep and the hoses no not lend themselves to visual inspection.
The mistake that I made the first time I checked the hoses was in pulling the vacuum with the key off. I was only checking for vacuum from the check valve to the N-75 valve. I was not checking all the way to the turbo. With the key on, I would have seen the leak, since this opens the N75 valve. Hind sight is perfect!
Hate to admit to a novice mistake, but it happens. I doubt that I will ever forget it either. I hope this helps someone. Whenever I use this site, I try to contribute a post as payment for the help that I have received. TDI club is without a doubt, the best site out there. (That is not intended to be a slam on the others, just my opinion.)
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Old September 30th, 2019, 13:05   #110
Baumjaeger
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Join Date: Feb 2015
Location: Vancouver Island
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Ok I had this issue vexing me for ages and as I had purchased the car with a new turbo I spent hours looking for vac and/or/boost leaks. Nothing. Farted about with EGR restrictor and block off plates. Nothing....limp mode would just keep coming back.
Got to where I was going to have a spare ecu reflashed and swap out engine harness.

Then a buddy with same car and same issues helped me make some sense.

The new turbo came from Mahle. So did his.

I swapped in my spare Garrett and while it’s only been a week and I know I am hailing the vw gremlins...I have not gone into limp mode.

If you folks that have replaced your turbos can chime in if they happen to be Mahle branded then that would be very interesting.
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