Passat Stalling when coming to a stop / slowing down
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  1. #1
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    Passat Stalling when coming to a stop / slowing down

    Hey guys-

    A little history on my 2000 Passat 1.8T manual transmission. Two weeks ago I left my headlights on overnight and the battery was completely dead in the morning. I was able to start it with a jump and drove to work just fine. I was able to drive it home and back to work the next day with no issues.

    Then, I got the Alternator Workshop message. As I was driving home it did the ABS fail, airbag fail.. etc and died on the side of the road. It was clearly the alternator. I replaced the alternator and everything is fine.

    Then, I picked up a new MAF to cure a MAF CEL that I've had for months. Installed a new air filter when I replaced the MAF. Went to the parts store and cleared the CEL and it hasn't come on since.

    So, a few weeks go by and the Passat is performing as expected.. until today. As I was slowing down to turn left the vehicle stalled, the battery light came on and I had to muscle the car to the side of the road since power steering went out. Once pulled off the road I was able to start and drove home.

    Then, I took the passat on a 50 or so mile trip to see a buddy in the next town. On my way home, I slowed down to change lanes (was going about 20) and it did the same thing. I had to muscle it in to a McDonalds parking lot. Once stopped it started as usual and I drove it the 50 miles home.

    Any idea what this could be? I know its not the battery because I didn't get the ABS fail, airbag fail etc etc when it died these 2 times. The engine just quit..

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  3. #2
    PZ
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    Still a good idea to scan it for codes, they don't always give a CEL. I would check all vacuum lines, check valves etc.. Also clean and adapt the throttle body.

  4. #3
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    OK.. I'll stop at the parts store and check to see if there are any hidden codes.

    Another thing I noticed is that when I put the transmission in neutral.. it usually goes to an idle RPM of 900. Most of the times it goes right to 900, sometimes it dips below. I don't remember this happening before. For whatever reason my eye is drawn to the RPMs as it looks a little "off" sometimes. Like it dips lower than I remember it.

    Crank position sensor maybe? Throttle position sensor? Someone out there must be thinking that's a classic case of...

  5. #4
    PZ
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    Classic case of a dirty throttle body.

  6. #5
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    PZ Thanks for the help

    I'm sure I can find how to clean the throttle body, but what did you mean by "adapt throttle body"?

  7. #6
    PZ
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    The throttle body is run by the computer. When power is removed, sometimes the physical opening of the throttle body does not match what the computer thinks it is.

    You can reset the computer with a vagcom, but you can do a cheap version that gets close by opening the hood and door. Turn the key to on (but not run) and wait 2 minutes. You will hear the throttle body moving.

  8. #7
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    It is the throttle body for sure. Can't believe no one else mentioned this!

  9. #8
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    I have an 03 1.8T AWM, but a friend who has an 04 AWM called and her car died out of town yesterday and she was told the problem is the throttle position sensor. I would just like some confirmation of what I think is correct. Is the TPS an integral part of the throttle body? From what I read above am I correct that the new throttle body will adapt itself to the ECM sufficiently without the vagcom "training"?

  10. #9
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    Hey guys-

    I cleaned the throttle body last night. It wasn't really THAT dirty. None the less, I cleaned it with throttle body cleaner and when I was done it was completely pristine.

    Today coming back from lunch it did it again. It doesn't do it ALL the time, but it does happen maybe twice a week. Any other ideas? I'll try resetting the throttle body with the hood / door trick tonight.

  11. #10
    PZ
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    TBA should do it, but if there are further problems, it should be scanned even if the CEL is not on.

  12. #11
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    I had a similiar experience with a vacuum leak on the PCV system. It was that jet valve on top of the engine. Most of the time the vacuum was enough to hold it together but sometime at idle the engine missed and stalled.

    Later on the L-shaped vaccum hose split open, the car would run fine above 1500 RPM but missed at idle. Apparently again, the vacuum was enough to hold the hose together at higher RPMs.

  13. #12
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    I'll check the PCV system vacuum tonight.

    I was out of town this last weekend and wasn't able to do the throttle body adapt procedure. On the way home from work the Passat stalled again. It did it on the highway this time as I was slowing down in heavy traffic, but I was able to immediately pull off. I took a good look at the RPM gauge and when I shift in to Neutral to coast to a stop the RPMs drop below the 900 or so idle and when rpms hit 0 the car stalls. I've realized that if I see this about to happen I can panic stomp on the accelerator and it won't stall out.. This by all means does not happen every time.. but about once or twice every week.

    So, tonight I tried the procedure. I opened the hood and the drivers door. I then turned the ignition key to "on". The throttle body made a high pitched whiny noise for about a minute. It then stopped making all noise. I kept the key in the on position for about 5 minutes, then repeated the procedure.

    Did I do this right? I was kind of expecting something to happen at the 2 minute mark. I don't think I heard the paddle inside moving.. just a whine noise.

  14. #13
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    Yes, you did it correctly. It's as simple as that.

    Fill us in on if it occurs again.

  15. #14
    PZ
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    On my ATW, that got the TBA at 98% when it was checked against a vagcom.

  16. #15
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    No dice guys... car died again today. What else can it be? Is it for sure Vacuum related now? Just try to hunt out any possible leaks?

  17. #16
    PZ
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    So no codes from the scan? If it is chipped, I would suspect a bad solder on the chipset. Otherwise, I would check the fuel pressure (usually dies on the highway) and as a last resort, change the engine speed sensor. That is one of the few things I have seen repeatedly stall an engine and not give a code for up to a year after symptoms begin.

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