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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 3 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.