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Virtual Wrench
Virtual Wrench, Master Tech
Category: VW
Satisfied Customers: 14612
Experience:  30 years/Master Tech. Foreign and Domestic
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Why does my car shut off at a stop light while idling?

Customer Question

My car sometimes shuts off at a stop light, car is idling, then just shuts off. Usually I have all power in lights, radio, etc. Just the engine. On the instrument panel, I have the check engine light and the battery light. Can you tell me why? Does it have to do with my car idling to low for RPM or do I need a new battery?
Submitted: 8 years ago.
Category: VW
Expert:  Virtual Wrench replied 8 years ago.


Does the battery lite only come on at idle?

Customer: replied 8 years ago.

Yes, the battery light actually only goes on when the car stalls, once I put it in park and then restart, it ALWAYS restarts no problem and all instrument lights turn off. Everything is fine. It's sporadic, I have had since May 07 and it's a 1999, but it's only stalled about 6 times. I have replaced timing belt a few months back, but happened before that too. IT's automatic.

Expert:  Virtual Wrench replied 8 years ago.


That would be normal for those lights to come on when the engine stalls.

This sure sounds like either a vacuum leak in one of the little vacuum hoses on the engine, or it could be the IAC valve (idle air control).

What is the year, mdel and engine size of this car?

Customer: replied 8 years ago.

1999 VW Jetta GLS-auto, 2L engine 4 cylinder

Expert:  Virtual Wrench replied 8 years ago.


This doesn't use an IAC valve for idle control, it uses a TPS (throttle position sensor) for one,,,to control idle.

The most likely suspect is going to be a vacuum leak somewhere under the hood. If you were to run it by pretty much any shop, they wont charge much at all to pop the hood and take a look around,,they will have a better idea of where to look.

At any rate, its not going to be a major repair at all, just tricky to find :-)

If you have further questions on this, please feel free to reply.

Happy Holidays!

Virtual Wrench and other VW Specialists are ready to help you
Customer: replied 8 years ago.
Just to clarify, on another website, they advised it could be one of the following:

Idle speed is incorrect
Fuel filter clogged and/or water and impurities in the fuel system
Ignition components damp or damaged
Faulty emissions system components
Faulty or incorrectly gapped plugs
Faulty spark plug wires
Vacuum leak in the fuel injection system, intake manifold or vacuum hoses

So you think it is the last option and can confidently rule out the others?

Thanks, ***** ***** help!
Expert:  Virtual Wrench replied 8 years ago.

You are very welcome :-)

The first line correlates with a vacum leak (idle speed is incorrect) the next ones i can definatly rule out, if it was ignition related or fuel related, you would have a hard time restarting it,,if at all.

If there are no vac leaks present, you might be able to just tweak up the idle.

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