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Q: Bank 1 running to rich and injector 1 contribution fault Intermittent.

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've been getting misfires at idle when the car is hot, on cylinder 1 only (i'll see cylinder 3 sometimes but it's very minimum)

When first starting the car from cold in the morning, it will stumble a bit and then will run fine. I suspect that's because the car is already running rich so there is leftover gas.

I have a VCDS that I have been using a lot to troubleshoot this issue and this is my constant reading at idle.

Code: Address 01: Engine (8E1 910 559 F)

10:48:35 Group 032: Lambda Control (Mixture Adaptation) -16.5 % Adaptation (Idle) Bank 1 Sensor 1 -3.0 % Adaptation (Partial) Bank 1 Sensor 1 -10.0 % Adaptation (Idle) Bank 2 Sensor 1 -3.3 % Adaptation (Partial) Bank 2 Sensor 1

10:48:35 Group 033: Lambda Control -3.2 % Lambda Control Bank 1 Sensor 1 1.938 V Sensor Voltage Bank 1 Sensor 1 -3.7 % Lambda Control Bank 2 Sensor 1 1.938 V Sensor Voltage Bank 2 Sensor 1

10:48:35 Group 054: Idle Speed Stabilization 782 /min Engine Speed (G28) Idle Load

My car has 201000 miles.
My car has an automatic transmission.

A: Hi and thanks for contacting YourMechanic. ...

Hi and thanks for contacting YourMechanic. What you are experiencing is a misfire detected in cylinder 1 and a random misfire in cylinder 3. This could be caused by either the fuel injectors not firing, the spark plugs fouling out, or a possible blow by ring issue. What I recommend to do is check the injectors to see if they are working. With the engine running, you could remove the injector harness to the injector and see if the engine drops in RPM. If the engine drops in RPM, then the injector is working. If the engine stays the same, then the injector is not working.

With the engine off, you could remove the spark plugs from cylinder 1 and cylinder 3 and switch them with another cylinder. This will make the symptom change to other cylinders if the spark plugs are causing the problem.

If the injectors are working fine and the spark plugs are switched and your engine still is having trouble, then you would need to do a compression test. Check the compression on the first puff and then max out the puff. The pressure indicated on the first puff needs to be half or more of the final puff. If it is less than half, then the rings are probably worn. If all the problems are tested and checks out okay, then I would suggest having a professional, like one from YourMechanic, diagnose the misfiring issue properly so that this issue can be resolved.

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