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My Jetta GL 2.0 2005 automatic transmission, struggles to start and it wont go past 20 mph when it does. It only starts if I step on the gas pedal while starting. It makes a weird sound just after the motor starts and sometimes it just turns off when I'm at a stop light.

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needs more details on why and how it doesnt go past 20 what does it do during idle? sounds like it might be timing or fuel related. –  agent provocateur Feb 13 at 22:37
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Does it throw any error codes? Check if anything triggered so called “limp-home” mode — in case ECU computer does not receive proper sensor data for air-fuel mixture, it switches to a sort of safe mode that is just enough to putt along. It should also run real rough. I had same issue when my MAF sensor went kaput. –  theUg Feb 15 at 17:50
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3 Answers 3

I had a vehicle once that would barely make it up hills and also wouldn't go more than 40 MPH or so. The vehicle was much older (1980's), though.

The problem ended up being that 2 of the 4 cylinders weren't working due to the spark plug wires had gotten old and weren't transferring the charge from the plugs to the cylinders.

While this is a possibility for your case, you left out a lot of details about your car's behavior so for more specific assistance try to include additional details.

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check your mass air flow sensor(MAF). It monitors the amount of air entering the engine. They often get dirty or simply begin to fail and the ecm can't correctly adjust the air/fuel ratio causing it to go into a limp mode in hopes of protecting the engine. Cleaning the throttle body wouldn't be a terrible idea either

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There are only three things that will reasonably cause this problem... (the fourth is very expensive... and very sad)

  • The engine is not getting enough air
  • The engine is not getting enough fuel
  • The engine is not burning the air and fuel it has

(Technically, there could also be something physically causing a very high load to be added to the engine's normal work. This would be something like a VERY bad transmission, a frozen wheel bearing, dragging the back seat behind the car, or something else very obvious, and very expensive. But enough of that.)

Why might the engine not be getting enough air?

  • The air filter (or some other part of the airway) is clogged
  • Something electrical has gone wonky and the computer is not giving the engine the right amount of air

Why might the engine not be getting enough fuel?

  • The fuel filter (or some other part of the fuel system) is clogged.
  • The fuel pump is not providing enough fuel (or enough pressure)
  • Something electrical has gone wonky and the computer is not giving the engine the right amount of air.

Without more details, it's kind of hard to guess which of these things might be the problem. I hope this helps you narrow it down!

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