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AudiGuru, Master Guild Audi Technician
Category: Audi
Satisfied Customers: 371
Experience:  Master Guild Audi / Master ASE Tech incl. L1 Advanced Level Diagnosis
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2004 Audi A4: it runs fine and idles..rough..Check Engine light

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Hi, I have a 2004 Audi A4 1.8 T (front wheel drive). Normally it runs fine and idles smoothly, but 2-3 times a day, when stopped it'll idle extremely rough with the Check Engine light blinking. Its even stopped running once, but restarted immediately. When I press on the accelerator, it runs smooth. Using a OBDII reader, I got the codes P0171, P0300, P0301, and P0302.
This sounds like bad ignition coils. I would replace all 4. I will be back in a few minutes with a price and place to buy. I also need to look up P0171.

P0300 is a random misfire fault. You get this any time the engine misfires.
P0301 is misfire on cyl. 1
P0302 is misfire on cyl. 2

The check engine light flashes because of the misfires warning you not to drive the vehicle because it can cause more damage.
AudiGuru and other Audi Specialists are ready to help you
Customer: replied 8 years ago.
Thanks for your help. Please let me know what p0171 is too. Thanks Chris [email protected]

P0171 is system too lean. This means you have an air leak which can cause a misfire.

Check these hoses. They go under the intake manifold. Look for oil or splits or listen for a hissing sound. Check these before you do the coils.


Here is the link for the coils.

You want Part# : 06B 905 115 R They are the latest and greatest coils.