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I have a 2004 Volkswagen Jetta and it won't let me go over 20 mph at times but also after a little while it starts to drive normally. I'm confused as this is my first car and I feel like the place I took it to is trying to play me. Has anyone dealt with this problem before?

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  • Welcome to Motor Vehicle Maintenance & Repair! Is the check engine light on? Did the place you took it to say there were any codes? If so, did they tell you what they are (the exact number code would be very helpful here). Also, until you get a direction, don't change out any parts ... I truly doubt this is a mass air flow (MAF) sensor from your description. Jun 21 '18 at 19:07
  • So you will be going 20mph, and when you press the gas pedal more, the car does not accelerate past 20? When this happens, does the car maintain a speed of 20mph, or does it feel like it the car starts to slow down?
    – sam
    Jun 21 '18 at 19:28
  • When was it last serviced? Is the air filter blocked?
    – Solar Mike
    Jun 21 '18 at 20:15
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    Possible the catalytic converter has failed and disintegrated, and the debris is blocking the exhaust. With the car in neutral, will the engine spin up to the max revs as you expect, if you blip the throttle? If it misfires and/or dies instead, that would suggest a blocked exhaust to me.
    – alephzero
    Jun 22 '18 at 10:21
  • Assuming this is an automatic transmission, could it be a transmission in "limp mode" and occasionally (when it behaves normally) it's not sensing a transmission issue?
    – Milwrdfan
    Nov 20 '18 at 22:16
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I'd suggest checking your spark plugs/glow plugs and your ignition coils.

You can also buy a cheap OBD2 Scanner from EBay and an app to use it with on the Google Play Store. It's not the best but it can read any Fault Codes and tell you what it's for. You can then research the Fault Codes online and try and pinpoint where the problem is instead of going to the Garage and having them check 101 things. The App I use is called MotorData OBD and for the Scanner just go on EBay and type in OBD scanner

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Sometimes you have to take the car back. when you have an intermittent problem, there is a chance that it will not make itself known at the garage. I would however take it somewhere else that can keep it a day or two and be able to drive it with a scope attached to the odb ii port. While in an actual driving situation they should be able to identify any out of range readings. It could be a number of things that can cause this and there is nearly zero chance of someone guessing the problem with the information you provided. You could have the transmission going into limp mode for example and that locks you into second gear. It could be a shorting wire on a coil. It could be a broken vacuum line that is opening and closing at a crack. There's just no way to know. I'm guessing transmission though. It has a solenoid pack on it and solenoids wear out.

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Check your mass air flow sensor it may be dirty or bad. It regulates air flow and fuel mixture to throttle body. This will cause the computer to go into limp mode to protect. Motor. Get some cleaner and spray it clean see if that works if not replace it.

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  • How does the MAF regulate the airflow going to the throttle body? Why are you sure this has anything to do with the MAF in the first place? Jun 21 '18 at 19:08
  • Here are some of the most common symptoms of a faulty mass airflow sensor: The engine is very hard to start or turn over. The engine stalls shortly after starting. The engine hesitates or drags while under load or idle. Hesitation and jerking during acceleration. The engine hiccups. Excessively rich or lean idling.
    – Randy
    Jun 22 '18 at 19:44

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