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Discussion Starter · #1 ·
I recently bought a vw beetle on craigslist and didn't notice until after that the car slowly goes up to
40 mph max. I went only and found that it could be the Mass airflow sensor, doing the tests it says to unplug the sensor and if the car works better then that was my problem. So I unplugged the mass airflow sensor and the car works perfectly normal leaving me to think that was the problem. So I stop in Auto zone and have them order the exact part for my car since my car is a diesel. Once i receive the maf sensor and install it, my car still responds slowing with the slow acceleration. I read somewhere that it could take some time for the computer in the car to adjust to new sensors. I kept the new sensor in for 4 days and still nothing. So now I'm completely lost as to why my car won't go any faster. Ive been reading some forums and it sounds like there could be a vacuum leak somewhere. But the thing is, I'm thinking it can't be anything other than the maf sensor. Because as I said before my car runs perfectly with the sensor unplugged. If anyone can please help me out that would be great, because this is my first car and i would hate to start from scratch.
 

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I would scan the car for trouble codes and see what comes up! A common problem with the TDI engine; is the egr/intake get clogged up, performance suffers and has to be cleaned out to restore the car to perform as it should. How many miles are on the engine?

Check out this thread for more info:

http://newbeetle.org/forums/1-9-liter-tdi/78857-2000-beetle-tdi-rough-pulsing-idle.html

More info and how to's about the carbon problem and cleaning process:

https://www.google.com/search?clien...e&ie=UTF-8&oe=UTF-8#q=tdi+egr+clogged+&rls=en

When it comes to MAF sensors; there are allot of cheap brands out there... stick with OEM BOSCH. You can find the correct part by searching with the Bosch website:

http://www.boschautoparts.com/vehiclepartfinder/pages/vehiclepartfinder.aspx


Here is a good site for TDI/MAF issues:

http://www.myturbodiesel.com/wiki/maf-sensor-faq-troubleshooting-replacement-vw-audi-tdi-diesel/

more info:

https://www.google.com/search?clien...=UTF-8#q=vw+maf+sensor+testing&rls=en&spell=1
 

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Billy is right, without scanning the codes, you can spend a LOT of money replacing sensors.

You neglected some key info, what year is the car, how many miles? Check Engine light on at all?

When you drive the car, do you hear a buzz or sucking sound as you accelerate? The ducting to and from the intercooler (passenger side of the engine from under the fender back to the intake manifold) is critical to proper operation of the turbo. If this duct is not secure or has cracks, the intake air will not make it all the way to intake and you will lose tons of power. just one thing to look at.

Good luck and keep this thread going, there's lots of help available here. Once you get it running right, your tDI Beetle will be a joy.
 

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Could be the N75 valve on the turbo
 

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Discussion Starter · #5 ·
The car is a 2001 vw beetle deisel it has 192,000 miles on it and the check engine light is not on but I did notice the ABS light is on.
 

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What are the trouble codes; do you have access to a obd II or VW/VCDS type scanner? :confused: You really need to check the codes; to give you some direction in your troubleshooting process. Have you checked the EGR/intake to see if it is clogged with carbon?
 

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I've never gotten a maf from autozone. It could be faulty. I believe it's the same part as a 2.0 gas motor. So it's possible to get a working part from a car in a yard. I'm in agreement that it's likely the maf since the problem stopped with it unplugged and the system using default values in place of data from the sensor. Is the air filter new? Using a cone ram/cold air intake?
 

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Discussion Starter · #8 ·
Does anyone still have any insights could it be the mass airflow sensor because the car does go faster with it unplugged. Or could it be a vacuum leak. I was thinking if it was a vacuum leak or a clogged intake or erg how does the car better with the mass air flow sensor unplug. Does the the car use the part of the car with it unplugged. Or could the new maf just be faulty.
 

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