Fourtitude.com - Power Loss Over 3000RPM, thermostat and temp sensor
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    1. 11-13-2019 05:59 PM #1
      Hi there!
      I am new to the forum because I just got my first jetta (2007 2.0l CITY model) and have had something weird come up. I checked through some of the other posts in this forum and could not find an issue exactly like mine—if there is, I'd love to know where to find it In short, I am losing power over ~3100 RPM regardless of speed (SAFE mode?). I do have a CEL light on due to needing a thermostat and temp. sensor (according to the dealer)... IS this something that would throw the car into SAFE MODE? The car drives fine and sounds normal below 3100RPM, and I can get it up to around 110kmph below3100RPM. However, once I hit 3100RPM I lose power and the sounds of the engine changes and can put the pedal to the floor and the car slows to around 60kmph with a steady 3100RPM. If I let off the the pedal for a bit then the engine becomes responsive again and I am able to accelerate again up to the same 3100RPM. Rinse and repeat.
      Thanks!
      Josh

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    3. Semi-n00b
      Join Date
      Nov 11th, 2019
      Location
      Cleveland, GA
      Posts
      11
      Cars
      2006 Jetta TDI, 2011 Jetta 2.0L MT.
      11-15-2019 11:02 AM #2
      I apologize but I am new here and am not familiar with "SAFE mode" in the gas jettas? Certainly the the diesels have "limp mode" when the boost system is compromised, and there is safe mode in the radio, but what do you mean safe mode on the engine?? Or are you asking if the power loss is due to some type of ECU limiting process which you are calling safe mode??

      This engine is pretty simple and basic. IME, power loss at "higher" rpms is usually a fuel or air restriction problem or a timing advancement problem (which would generally throw a code). The first two would could be restricted air filter/injectors/fuel filter while the last could be a sensor problem. Also, spark plugs could cause such a problem if they are old and the gap has opened up. In the more extreme cases, a clogged catalytic converter could cause such issues, but again, that would generally throw a code.

      Whenever I get a new (to me) car, I first go through and replace all the "consumables" in the car - spark plugs, air filter, fuel filter, plug wires, brake fluid, coolant etc. It puts everything in a known state. This engine does have somewhat of a reputation for consuming spark plugs and sensitivity to fuel quality (not octane but "quality").

      Hope that is helpful, and certainly I would do something about the thermostat and temp sensor, if the engine is overheating, that can certainly cause many problems.

      Good luck.
      Larry A
      Last edited by terpsgeorgia; 11-15-2019 at 04:43 PM.

    4. 11-18-2019 01:27 PM #3
      Hi Larry,

      Thanks for the response. By "SAFE mode" I just mean some ECU limiting process—sorry for the confusion.
      Although this car is likely due for plugs and filters, the strange thing is that the engine drastically loses power right around 3100RPM. So long as I stay just under that number, no problem: acceleration and speed are fine. Does that sound like a known issue or ECU limiting process? I also had the car scanned at a VW dealership and apparently it was only throwing codes for the thermostat and temp sensor—which I plan to replace asap... I am just trying to findout if there is something more seriously wrong with the engine alongside the temp sensor and thermostat that may cause power loss before I start putting time and money into it (I am hoping that replacing the thermostat and temp sensor might fix the acceleration issue). I will also try to get it scanned again in the next couple of days and post back.

      Josh

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    6. Semi-n00b
      Join Date
      Nov 11th, 2019
      Location
      Cleveland, GA
      Posts
      11
      Cars
      2006 Jetta TDI, 2011 Jetta 2.0L MT.
      11-19-2019 12:21 PM #4
      I would not really focus on the specific RPM at which things are becoming problematic. There is no turbo and only 1 intake and 1 exhaust valve in each cylinder. So there is nothing special happening at some rpm to increase performance.

      The RPM is probably not important but rather symptomatic of the point were some restriction becomes critical to engine performance. I would start with new air filter and new fuel filter. Those are easy to change and cheap but failure can create restrictions easily. Then move on to some of the more difficult ones. Would also pull a spark plug and check its condition. Not just the state of the gap but also look at the color which can tell you what is being restricted by its color. Here is a link to reading spark plugs. https://www.championautoparts.com/Pa...ark-plugs.html

    7. 11-21-2019 12:50 PM #5
      Fair enough, I will start by swapping those out, and I will keep you posted on any updates! I appreciate the link to the spark plugs site.
      Thanks again,
      Josh

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