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My 2001 Cabrio only idles. I had a mass/air error code, however I changed this and had no luck.

I swapped one from a running VW, the other VW ran normally, but mine didn't.

I had the shop read codes: mass/air and transmission and speed sensor. I changed the transmission and the speed sensor, but it still only idles. Now i get a TPS code. Swapped out TPS with running VW, and it fixed it. I took it to the VW shop to get ecu flashed/reprogrammed after paying for 1 hr repair. The mechanic said the TPS was bad, so I swapped it with another one, however the other VW is still running well and mine only idles. I have checked the wires and the ground. I'm out of ideas now.

Can anybody please suggest what could be wrong? Do I have an ECU problem?

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    I wonder if the TPS isn't being acted upon? Assuming this is attached to the throttle plate, wondering if that isn't moving the TPS? Just spitballing. – Pᴀᴜʟsᴛᴇʀ2 Mar 9 '16 at 2:37
  • "Idles only" as in "won't accelerate"? – I have no idea what I'm doing Mar 9 '16 at 10:58
  • idles only. if gas peddle is pushed the engine dies. if you clear the tps code it runs and accelerates fine for around 5 min then get code again. have changed throttle body with a running vw both work fine and no codes on other vw. same with mass-air sensor – schoolie1 Mar 10 '16 at 0:16
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    Can you confirm the throttle plate works when someone presses the pedal? What was the TPS code? voltage high? low? circuit? When the car encounters a TPS/APP/ETC code it usually goes into a limp mode. – Ben Mar 18 '16 at 21:15
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    Have you recalibrated the throttle pedal? There is a recalibration procedure to follow on these cars. If that has been done, and the throttle body is clean and free from debris, my guess would be voltage is leaking onto the TPS earth from somewhere? Perhaps a fault loom. – Steve Matthews Apr 5 '16 at 12:19
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It sounds like an ECU problem. I would suggest the following, which I did on a VW which behaved similarly.

Start with engine idling, in first, and progressively shift up (use hills, whatever) to 30 MPH. At that point the cruise control will work. Engage, and use the increase speed button to establish operation at a speed which is above idle.

If that works, then things point back to the TPS, and since you have eliminated the TPS, the ECU's ability to process the TPS (digital) signal, or the ECU's interface to the TPS, or wiring.

Using the cruise control you can establish that the ECU can command the engine to more than just idle power, and you incorporate the speed sensor, etc.

As a side note, this technique was used to transport the car several hundred miles on interstates, until a repair could be done, so it is an effective get home strategy with a failed TPS.

Addendum #1: I would suggest that you try running your car without the TPS. Specifically use the technique I outlined. (It is easier with a TDI, however.) Get your car up to 30 MPH by shifting through the gears with the engine idling. Then engage the cruise control. Use the up speed button to control an increase in speed. The brake pedal will disengage the cruise, as usual. If the cruise control effectively controls the engine, then your faults point to the TPS. Having said that, the TPS wiring might be intermittent or the TPS interface in the ECU might be intermittent. Hopefully this helps you further diagnose things.

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