Quote:
Originally Posted by larchamb
Original code was P219A
They also threw GHQ42 at me, not sure whether its related.
Will find out more on Tuesday!
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P219A is
air-fuel ratio imbalance. I am now thinking much less that the dealer is full of sh*t, and more that they may be on to the problem. GHQ-anything is the wrong format for an OBDII code, so I'm going to assume that's a mis-transcription and ignore it.
In your OP you told us the dealer said
"something about an engine imbalance." I was initially skeptical, but seeing the code, I now see that it was a legitimate attempt to relay information, buried in a mis-transcription. However, given the nature of your post, I take it you are not well-informed. Let me fix that.
If the car is running very rich, it will do the following:
-throw that code,* and
-foul the plugs.
* In order for the code to trigger, and the plugs to foul, the engine must be running richer than commanded. (as opposed to leaner than commanded, which would have made different, albeit more exciting, issues for you)
The ECU commands a given air-fuel ratio at a given RPM and engine load; Load, defined as the mass of air entering the engine per rev. The ECU uses sensors to calculate the load, (one sensor for engine speed and a number of sensors to approximate airflow), and opens the fuel injectors by applying power to them for a calibrated amount of time (called the injector pulsewidth) to deliver a calibrated amount of fuel.
The ECU monitors how well it's doing it's job via an oxygen sensor in the exhaust, the readings from which can be used to calculate the air-fuel ratio of the burned gases coming out of the engine.
In fact, under stable conditions, your ECU uses the information from the O2 sensor to correct its fuel delivery schedule, and get closer to the target air-fuel ratio. This is called closed-loop correction.
Following me? good.
In order to throw the code, the input from the O2 sensor must be out of the acceptable range - either rich or lean. If the sensor is bad, it could throw the code when everything is otherwise just fine. BUT your plugs are fouled. That tells us three things.
1 - The engine is, in fact, running outside of the acceptable air-fuel ratio range.
2 - It is running unacceptably rich, not lean. Ergo, your plugs are fouled.
3 - The oxygen sensor is working correctly. This is
im-por-tant because a faulty O2 sensor can cause a rich/lean problem by itself... But that's a closed-loop discussion for another time.
From the information I've already given you, there are 2 possible answers:
1 - Injector or other fuel delivery problem (You have 8 of them, 4 port, 4 direct, and 2 pumps. Each is what engineers like to call a single-point-of-failure for the entire system.)
2 - Air sensor problem (likely the Mass Air Flow sensor, [MAF] as that is the primary input to the ECU for air flow)
There are many ways to narrow down the problem from there. For example, your dealer said plug
S were fouled... I'm assuming that means all of them. That fairly well rules out a single injector. P219A means imbalance in bank 1, but that's funny because despite having 2 banks of cylinders, this engine has only 1 oxygen sensor, and therefore, not "bank 2" code at all.. Yep, no P219B for you.
This points to a problem in all the cylinders, which points to an air metering problem.
This engine uses a hot-wire MAF, the operating concept of which I will not take the time to explain. Suffice it to say, any increase in electrical resistance in the MAF circuit (loose wire, fouled contact, chafing, damaged or broken housing, or just poor quality control) will cause the engine to think there's a whole bunch of extra air coming in.
Just theories... All of it.