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Discussion Starter #1
Hello all. I'm reaching out because after extensive research via these forums, I'm at a point where I need assistance. Here is what's happening with my wife's 2005 2.0L (BEV) new beetle.

The car started experiencing stalling issues once the weather got hot (88-100 degrees F), and the a/c was running. Symptoms never started right away, but after driving the car for 15-20 minutes with the a/c on, the car would stall as if it isn't getting fuel. I purchased the Xtool VAG-401, and began looking into the fuel trim. When the car isn't experiencing stalling issues the values are as follows:

BLOCK 32
Adaptation (Idle) Bank 1 / Sensor 1 - 1.69%
Adaptation (Partial) Bank 1 / Sensor 1 - 0.00%

BLOCK 33
Lambda Control Bank 1 / Sensor 1 -
Sensor Voltage Bank 1 / Sensor 1 - 1.50V


These are the values when the car is stalling out:

BLOCK 32
Adaptation (Idle) Bank 1 / Sensor 1 - Fluctuating between 0.00% and 26.00%
Adaptation (Partial) Bank 1 / Sensor 1 - 0.00%

BLOCK 33
Lambda Control Bank 1 / Sensor 1 - Fluctuating between 6.25% and 25.78%
Sensor Voltage Bank 1 / Sensor 1 - 1.76V

*** It should also be noted that I pulled the codes once I got the VAG-401 and these were all the codes that came up.

19497 - Powertrain Databus / Implausible engine temp
16804 - Catalyst System, Bank 1 Efficiency below threshold
17925 - Power supply relay for ECU (J271 or J363) electrical malfunction
16840 - Evap System, Very small leak detected
16555 - Fuel Trim, Bank 1, System too lean
16684 - Random multiple cylinder misfire
16687 - Cylinder 3 misfire
16688 - Cylinder 4 misfire

I then cleared the codes and the only one that returned the next day was (16804). I cleared this code again, and the car wasn't having the stalling issues according to my wife. She also wasn't running the a/c. Today I took her car out and ran the a/c. Car ran fine until I got home and hooked up the VAG-401. Then it started the stalling symptoms, but wasn't generating any codes.

It should also be noted that I've recently replaced the Thermostat, Engine coolant temp sensor, and Spark plugs. The plug wires look OK, and I also cleaned the MAF sensor. Air filter is pretty new as well.

My first thoughts are definitely trying to locate an vacuum leak. I'll then troubleshoot the O2 sensors, and fuel pump relay. Being that the car has generated codes 16804, and 16840 in the past, I feel as though the ECM is compensating by adding more fuel because of an air leak, or incorrect reading through the O2 sensors. Being that it only happens when it's hot, and the car draws more of a load is what's stumping me. Any help and thoughts are greatly appreciated!
 

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Lots of possibilities. I woudl start working down the list of possible solutions; listed in the ross tech lean code definition.

http://wiki.ross-tech.com/wiki/index.php/16555/P0171/000369

Rough idle and stalling; on the 2.0L has been commonly related to a dirty throttle body. A full clean of the throttle body and then run the alignment process, can really help, many times.

For the lean codes; keep your eye on fuel trim levels, anything beyond + or - 10%, is out of nirmal range.

I would start with basic baseline testing; a fuel pressure test in particular and that way you rule that out.

Fuel pressure testing info:

https://workshop-manuals.com/volkswagen/new_beetle/l4-2.0l_(avh)/maintenance/tune-up_and_engine_performance_checks/fuel_pressure/system_information/specifications/

Fuel trim info:

http://wiki.ross-tech.com/wiki/index.php/Fuel_Trim_Info

Check your fuel trims, clean/adapt your theottle body and do the fuel pressure test. We can go from there. Thanks! :)
 

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Discussion Starter #4
Thanks Billymade! I had been referencing the Ross tech index to search all of those codes, and find common denominators to start the troubleshooting process. I agree that doing the fuel pressure test should be one of the first steps as well. Once I rule out the fuel pump, then I can work forward by testing the voltage at the fuel pump relay. If I can rule out a fuel problem causing my lean issue, then I also know for a fact that it's pointing to a vacuum/air leak somewhere. As for the stalling I've combed through the threads and found that there have been multiple culprits from crankshaft position sensor, to the ignition coils. One step at a time!
 
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