[Arcanox]

I'm making this thread to help track people's success rates and stories regarding the TSB to fix engine backfire. I had it applied yesterday at Castle Chevy North in Elk Grove Village, IL. Dealer was helpful for the most part, had my car by the end of the day, and got a shuttle ride from the dealer back to work after I dropped it off. They also charged my battery up all the way when it was done. The unfortunate part for me was that the labor was not covered under warranty (yet), so I had to pay $150 when I picked the car up again. Not terrible, but it seems like Chevy should be the one paying since it's a design flaw that caused the problem in the first place.

I've driven for probably 30 miles total on gas power since getting it fixed, and I haven't heard the noise a single time since. The engine seems to start at idle power and wait a second before revving up now, as opposed to starting and immediately revving before the fix was applied. I'm guessing the higher startup throttle let some unburned vapor or gas to reach the hot exhaust system prior to this fix, causing the pop noise.

I may be a bit overzealous, but it seems like my mileage may have improved slightly. On days that I travel further for lunch, my engine usually comes on as I'm leaving the highway on the way home, about 6-7 miles away from my house. It came on about a mile later than usual today, but still in the general area. I've usually been getting 45-ish MPG when I get home on those days, but today I had higher:

I left it unplugged and I'll go back out when there's less traffic to do some more driving and get a larger sample size.

 

[Bretsuaz48]

Are you out of warranty?

 

[Arcanox]

Are you out of warranty?

I certainly shouldn't be. I bought the car almost exactly 2 years ago as a Certified Pre-Owned. It still had part of the "New Car" warranty left, which I believe was a 3-year warranty (so nearly up) and the salesman guaranteed me that the CPO warranty would not take effect until the new car warranty lapses. The Voltec warranty should be 8 years, which is what this TSB is covered under (see this post).

 

[Arcanox]

I'm voting that I didn't have an improvement in MPG, even though it does seem like my average has gone up a tiny bit. I'll have to drive it for longer to tell for sure. I definitely notice it being smoother and less backfirey than before.

 

[fishyducky]

I had the TSB done to my 2017. Haven’t heard the backfire since it was completed. I did notice better mileage as well but haven’t driven the car on gas long enough to make a definitive conclusion. Chalked it up to good weather thus far.

 

[Andy00778]

I voted no, that the update did not fix the backfire issue. To clarify, the car does backfire consistently on one day, and consistently not backfire the next. I drove out of town yesterday I noticed it on several instances ( battery 90%+) of the backfire. Driving home today there were no signs of backfiring and we must have stopped 20+ times at lights etc.

Was going to take it back in to the dealer, but I suspect it won’t do it on command.

Anybody else notice this. Both days were about 50-60 degrees F.

 

[fishyducky]

I voted no, that the update did not fix the backfire issue. To clarify, the car does backfire consistently on one day, and consistently not backfire the next. I drove out of town yesterday I noticed it on several instances ( battery 90%+) of the backfire. Driving home today there were no signs of backfiring and we must have stopped 20+ times at lights etc.

Was going to take it back in to the dealer, but I suspect it won’t do it on command.

Anybody else notice this. Both days were about 50-60 degrees F.

Yes, I got a backfire today. Just one, but still got one.

 

[Arcanox]

Man...that's pretty disappointing. I wonder if the programming didn't "stick" for you guys, or maybe it's just a per-car thing. I drove 40 miles on ICE today in stop/go traffic and never heard it; I've made that same drive countless times before and heard it all the time. I'd suggest taking it back in and complaining more if you have the time to do so.

 

[Tomt]

It appears to have fixed the backfire for me and the genset does appear to be a little smoother, but no change in MPG or range.

 

[Andy00778]

Mine is scheduled back in on the 15th, told me to bring it in with zero battery range.

Man...that's pretty disappointing. I wonder if the programming didn't "stick" for you guys, or maybe it's just a per-car thing. I drove 40 miles on ICE today in stop/go traffic and never heard it; I've made that same drive countless times before and heard it all the time. I'd suggest taking it back in and complaining more if you have the time to do so.

 

[jbakerjonathan]

I certainly shouldn't be. I bought the car almost exactly 2 years ago as a Certified Pre-Owned. It still had part of the "New Car" warranty left, which I believe was a 3-year warranty (so nearly up) and the salesman guaranteed me that the CPO warranty would not take effect until the new car warranty lapses. The Voltec warranty should be 8 years, which is what this TSB is covered under (see this post).

You got that guaranty in writing, right? Car salesmen often change dealerships. If you don't have the guaranty signed by the manager, not the salesman who can't speak for the dealership, go back and try to get the guaranty signed by the sales manager. Good luck.

 

[jcook01]

We had our TSB backfire fix applied many months ago, late spring, and have only noticed one instance of backfire since the fix.

Before the TSB we were almost guaranteed a backfire during each green light.

The GM fix appears to be working as designed.

 

[Andy00778]

Second time around for backfire TSB fix

Second time back at the dealer for this issue, I voted No, that the TSB did not fix the backfire issue. I suspected that they had not updated all the modules during the first visit in July

Sure enough, they found updates that had not been applied. Hope this issue is fixed now

 

[Geert Aerts]

Seems like this TSB fixed my backfire noise.

Be prepared for resistance from the Chevy dealer. At first the service advisor asked how often I put gas in. I said enough since I sometimes have to make long trips. Then he said I might have gotten bad gas and I said it's been doing it for 30,000 miles. Then they said mine isn't doing it. Then they said all the Volts do it. So I said if all the Volts are doing it, mine is, and there is a way to fix it. I had the car in for another warranty fix and refused to pick up the car from the dealership until they applied the TSB. After several days they claimed they contacted GM and got authorization to do the TSB and I could pick up my car.

 

[Andy00778]

I saw a post from GM direct on this subject and it’s covered under the emissions warranty. You shouldn’t need any special request to get it done and it should be covered well beyond the b2b warranty, as the emission warranty is much longer.

 

[RodSlinger]

I had the TSB done yesterday when I went in for my first 12k mileage service. The backfire is definitely gone and the engine does seem to idle smoother and quieter when running. Not sure about any mileage improvement as I rarely drive enough on gas to compare. I think we add back about six gallons every four or five months.

Of course the dealer put the 3,000 mile service reminder decal on the windshield. I think not....