Replaced battery and all heck broke lose
 

Hello Audi Friends!

Over the past few weeks, my battery was showing signs of failing. Every day my engine would crank a little slower. On its final day, I just got a series of clicks. I received a free replacement battery as the failed battery was only 23 months old. Installed the new battery, fired up the car and it was as if the vehicle was possessed. The vehicle was running but was shaking pretty well. The stability control light came on (I suspect due to the shaking) along with a flashing check engine light. I didn't allow the vehicle to run more than a few seconds as I was somewhat surprised and shocked. I attempted to "reset the ECU" following a few online guides that other Audi owners had success with. However, no joy here. Still ran terribly! I noticed that the engine light flashed 27 times for what it's worth.

I had the vehicle towed to the shop where I have all my Audi maintenance performed. They've had the vehicle for two days and are somewhat stumped. They're seeing a series of errors included misfires on cylinders 1 and 3. Interestingly enough, the solenoids have tested good (or in other words, it appears that the solenoids aren't the problem).

The car ran flawlessly up until the moment the battery was replaced. Good power, no hesitation, very even RPM at idle.

Does anyone have any idea or suggestions on what the mechanics could check?

VEHICLE SPECS: 2006 A6 Quattro 4.2l

Thanks everyone!

Are there any codes?

The car is throwing the following codes:

P0301 - Cylinder 1 misfire
P0303 - Cylinder 3 misfire

Injectors are confirmed good, coils were confirmed good, plugs look good.

Mechanic is leaning toward a timing issue. I just see these expenses spiraling out of control and in the end, I'll still have a car that doesn't run.

Thanks so much for any and all help.

If they think it is timing problem, using scan tool to perform basic setting to check crankshaft/camshaft timing, left and right head exhaust/intake camshafts timing. Don't forget to also perform engine compression check. Main timing chain problem will effect both left and right banks not just the cylinder 1 and 3 on bank 1. The right bank exhaust/intake camshaft chain problem will affect right bank but most likely will cause misfire to cylinder #2 too.

Oak, thanks for the detailed recos. I'll follow-up with the service team and will report back.

So this is interesting. I just spoke with the local Audi service department. I explained the battery situation and how the car is running--err not running--post-battery transplant.

With some hesitation, he shared with me that the A6 has a standalone battery management system that is calibrated to the specifications of the original battery. If the battery specifications change at all, the battery management system must be recalibrated. In addition, apparently Audi's replacement batteries contain technology that communicates with the battery management system and without the technology, the car will not run or will run poorly (not sure I buy that part). He stated that it's not unusual for the car to sputter, misfire and throw codes if the car isn't programmed with the new specifications.

Here's the kicker, there weeks out and the cost would be $500-700.

At this point, I'm tempted to purchase a new battery from Audi and install it myself just to see what happens.

Have someone code your battery for you so the BEM knows there is a new battery. Eliminate that possibility.

If I replaced the current battery with a battery that matches all of the specifications of the original battery, would it likely be okay? What programming would there be outside of voltage, battery format, cold cranking amps, cranking amps and capacity?

that is a good place to start, but won't tell the power management system that you have a new battery.
this requires coding.
easiest is the +1 serial number hack.
visit the ross-tech website for the A8D3 platform battery replacement.

UPDATE: I confirmed with the dealership that my make and model requires coding on the event of a battery change. I'm swinging by the stealership right now to purchase a battery, the contains a BEM code, and will have my mechanic perform the necessary coding using VCDS.

Fingers crossed that I'll be driving my car again this evening. Updates to follow.