Something is amiss with our 2013 CMS A4, automatic transmission, 14K miles.

Three times in the past few days under moderate acceleration at about 40 miles an hour it felt like the engine misfired or backfired three quick successive times.

It is very noticeable… The acceleration was interrupted, the whole car shook, and there was what I would describe as a muffled popping noise, perhaps the engine backfiring. I am under the impression that when the engine misfires, the check engine light is supposed to be turned on, but that did not happen.

I recall a couple of years ago on this forum owners were complaining about their cars stumbling under acceleration, and if I recall correctly, there was a software update. But I have not heard any complaints like that in a long time, our car is only 10 months old, and it is only started happening in the last few days.

I have not taken it to the dealer yet because it happens infrequently, and no doubt the response Will be that they can't replicate the problem. Especially given that there has been no check engine light, I would assume it will not be easy for them to diagnose the problem.

Anyone recognize the symptoms? Thanks in advance for your help.

 

I'd still take it in. The computer logs much more than you think even if a check-engine light hasn't come on.

You are using good gas, right? No potential for water in the lines?

 

Thanks for responding.

Yes, we always use top-tier fuel. Of course, that does not guarantee that we did not pick up a bad tank of fuel. I was thinking that is not the problem given that it only happens once every couple of days. We will buy our fuel next time at a different station, and if it continues, then I guess we can rule out bad fuel.

I am wondering if it is related to the problem that we have had with his car with rough idling. Even though we always use top-tier fuel, if we do not regularly add a bottle of Techron the idle quality quickly deteriorates. We never had to do this with the 2012 that we had.

Unless the problem gets worse, I suppose we will just mention it to the dealer when we bring it in for the next oil change, which will be soon. Was just wondering if anyone else had experienced this… I don't recall anyone else on this forum mentioning a similar problem.

 

I wouldn't let it go past the next tank of gas. What you are experiencing isn't normal.

 

I also wouldn't wait to long to bring it in.. Has the problem happen more then once? I would also bring up your rough idle to the dealer as well..

 

Hmmmm...
The techron doesn't clean the valves, so it must be affecting the fuel in some way.
I would say carbon buildup, but your mileage would convince me otherwise

 

Search for "stumble" and look at some old threads. This was common on the 2011's and early 2012's. I believe the thermostat housing was the culprit and resulted in a BMW voluntary recall. My updated replacement thermostat and water pump failed on my 2012 so it's possible yours is bad as well.
I know they don't seem related, but again search for stumble and read some old threads to determine if those symptoms are the same as what you are experiencing.