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TDI 101 Got a simple/basic TDI question? Are you a newbie (new to the forums). Feel free to post your question here.

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Old April 5th, 2011, 05:22   #16
oilhammer
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Correct, you need to see what the MAP sensor is actually reading before you proceed to throw expensive parts at the car. That was what I was getting at. Sorry, did not notice your post before .

I have replaced a couple of these sensors, and the symptoms were NO power (at all), because the ECU places the engine in limp mode right away if it cannot see the MAP values, and they always had a DTC set.

Chances are you do not need a MAP sensor, like 99%. Cleaning it won't do anything, it is already always covered in oily mist anyways.

Grab an appropriate scan tool, and drive the car and monitor actual and requested boost... you'll know right away if the MAP is doing its job.
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Old June 15th, 2011, 14:08   #17
aai2on
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Default Update - Wasn't the boost pressure sensor

VW Dealership thought it was the boost pressure sensor. NOPE

Currently the vehicle is experiencing lag on acceleration then cuts out until you give it more acceleration. Then it will get going. I put in a new air filter and cleaned the MAF. Slightly better at first, but the problem seems to be getting worse. We are noticing that during driving, you can feel the vehicle with small lags but continues driving.

Latest development. Car seems to have gone into limp mode. Would only do about 15mph. We took it to a good friend (mechanic) He says the throttle position sensor is reading high all of the time. He isn't getting much for reading, etc. I really don't want to take it back to dealership. They are total idiots (Las Cruces, NM ) My wife loves her car and needs it fixed. (Note: I know very little mechanic wise)

Any help is appreciated.
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Old June 15th, 2011, 14:28   #18
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Quote:
Originally Posted by oilhammer View Post
.... [smart guy stuff] ....

Chances are you do not need a MAP sensor, like 99%. ....[more smart guy ramblings]....

Grab an appropriate scan tool, and drive the car and monitor actual and requested boost... you'll know right away if the MAP is doing its job.
I think this guy has a good suggestion.
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Old June 15th, 2011, 18:26   #19
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Why is it when you give people advice, they ignore it, waste more money on parts, and then ask for more advice?

I don't get it.
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Old June 16th, 2011, 05:55   #20
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Why is it when you give people advice, they ignore it, waste more money on parts, and then ask for more advice?

I don't get it.
Me neither. You can lead a horse to water, but can't make him drink.
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Old June 22nd, 2011, 09:57   #21
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Still not getting any codes out of the engine. Going to try the cage mod and see if there is any change in performance.
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Old June 22nd, 2011, 10:35   #22
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oilhammer - I didn't ignore what you recommended doing. My mechanic and his $10K scanner isn't getting any error codes. He is running it in generic mode as he doesn't have VW unlocked I asked him again about the MAP codes and he said he would try it again. I specifically asked him to check the requested versus actual boost readings. Sorry for the inconvenience.

Should I just go buy the vag-com for my car and do it myself? We tried the new diag at the chevy dealer, but didn't get anything new (1.5 hrs x $75 to my mechanic) Not sure why he hasn't or how much it would cost to unlock the VW codes to his system...
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Old June 22nd, 2011, 10:47   #23
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Just because there are no DTCs, doesn't mean there could not be some issue, nor does it mean there is no useful data to be garnered from a proper scan tool.

I'd be willing to be VCDS can do more than his $10k scan tool on your Volkswagen.
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Old July 6th, 2011, 21:32   #24
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I don't know if this provides the information we're looking for. This was a quick try. Used 003, 011, and 115.
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Old July 6th, 2011, 22:36   #25
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IIRC, it is a 5 volt variable resistor. It COULD be tested outside IF you had a bench power supply, knew the connections and measured the output based on the pressure applied.

I've done this on GM MAP sensors. Used a PC power supply for the 5 volt source.

The VAG charge pressure sensor is similar, a 3 pin sensor which is a variable voltage "ladder". Meaning the voltage at terminal 2 is dependent on the pressure.

Since it measures the pressure over atmospheric, there is a vent on the outside. If this vent is clogged, there will be issues.
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Old July 7th, 2011, 08:47   #26
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Quote:
Originally Posted by aai2on View Post

Currently the vehicle is experiencing lag on acceleration then cuts out until you give it more acceleration. Then it will get going. I put in a new air filter and cleaned the MAF. Slightly better at first, but the problem seems to be getting worse. We are noticing that during driving, you can feel the vehicle with small lags but continues driving.

Sounds like the Typical PD Lag that everyone seems to have and spends months of their lives trying to figure out. All while never accomplishing anything. It feels like it builds boost, a "valve" opens and the boost drops but the power takes off, and then it begins to build boost up again, in a smooth fashion. It even looks that way on a Boost Gauge.

Some seem to like to put zip ties on them, and it reduces it, but that's a band-aid at best. While thinking about all the theories that have flown around on here, I think it is better while cool, and worse while hot hot.
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Old July 7th, 2011, 10:15   #27
aai2on
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Was the zip tie thing one of the hacks? At this point I am willing to try anything to get it to run better. The wife hates it, and when you take off, it seems to bog down. Driving in manual shift mode resolves the issues (into 2nd and 3rd gear)
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Old July 7th, 2011, 10:20   #28
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Originally Posted by jcrews View Post
You can test everything relevant with VCDS using run-up tests and basic settings mode. You should also test the vane actuator with a vacuum pump while visually watching it as well as having a helper watch VCDS for the reported position.

The MAP sender is solid state and is not affected by dirt, oil, etc. The only thing that can go wrong with it is if the transducer itself goes bad due to a defect.
I almost hate to ask, but where is the vane actuator located on a 2006 Jetta TDI? There is a component on top of the turbo that looks similar, but I don't see anyway of testing it without removing it.

There are other articles that seem to indicate you can see it from under the car... (I have the VCDS if you can tell me which is the appropriate test code to use)
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Old July 7th, 2011, 22:22   #29
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I'm sure if you search zip tie mod in the a5 forum, you'll find all the info you need, if that is what your talking about.

Below is my interpretation of whats going on.

It essentially slows down the building of boost, and it seems the computer has more time to reduce the boost spike and add fueling. Once your past that spike the vnt vanes aren't trying to build boost so rapidly and can easier and more smoothly make minor adjustments to the amount of boost requested vs actual. On full throttle and most in between the turbo is not trying to make maximum boost, its trying to hold at a certain pressure. If it were to continue trying at maximum vane angles, it would seriously overboost. The zip tie seems to stop it from initially building so much boost, thus getting you past that lag... now why the computer initially wants so much boost without the fuel, I'm not sure.

I've had that lag for a long long time, but it doesnt bother me much at all. I've stared at the boost gauge and played with it for more time than I ever should have. That is the conclusion I have come up with.

Best way I can figure of getting rid of it, is a bigger turbo ! Haha

Last edited by AndyUpNorth; July 7th, 2011 at 22:25. Reason: formatting
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Old July 9th, 2011, 22:48   #30
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Thanks AndyUpNorth. I will try the zip tie thing.
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