Hot restart misfire

YESSICALEON11

MEMBER
2009 AUDI A4
2.0L
4 CYL
TURBO
4WD
AUTOMATIC
89,700 MILES

Car runs greats when cold but misfire with blinking check engine light when is started hot, the blinking check engine light goes away by giving it gas. Spark plugs and coils were replaced already. When started hot RPM go up to 1,000 and then settle down to about 780 and that is when the check engine light starts flashing.

5 Replies

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

Hello,

This sounds like an engine coolant temperature sensor is going out, but to be sure lets run the codes by following this guide.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please run down these guides and report back.

Cheers, Ken

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Tuesday, September 18th, 2018 AT 12:30 PM

YESSICALEON11

MEMBER
3 POSTS

Codes are P0300, p0303, p0302 and sometimes p0301. I also noticed on the scan tool that when you start the engine while is warm it goes to open loop fault and the O2S11 is reading negative or only goes up to 0.0002. When it goes into open loop fault that is when the check engine light starts flashing. Thank you

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Tuesday, September 18th, 2018 AT 12:47 PM

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

I have seen oxygen sensor short out causing the problem you have described. Let's disconnect the sensor and drive the car to see if check engine light acts the same.

Here is a guide and diagrams below to show the oxygen sensor location:

https://www.2carpros.com/articles/how-to-replace-an-oxygen-sensor

Please run down these guides and diagrams and report back.

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