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Does your Gen 2 Volt make this clank?

  • Yes

    Votes: 41 51.3%
  • No

    Votes: 39 48.8%

Sporadic clank sound coming from rear when ICE kicks in, sometimes (25% of the time).

24K views 126 replies 41 participants last post by  quirkySquirt 
#1 · (Edited)
Had my 2016 since 12/2016 and have experienced this issue ever since. 21,000 miles on the car, only 1,500 ICE miles. Had Chevy look at a year ago, said it was normal. I know it's not. I'm having them look at it again. If it happens, it happens at the exact same time the ICE engages, no other times.

Anyone have the issue?

Update: see Chevy forum response in replies below. They explain the noise is normal, but can't say what makes the noise or why the noise is made.
 
#2 ·
Had my 2016 since 12/2016 and have experienced this issue ever since. 21,000 miles on the car, only 1,500 ICE miles. Had Chevy look at a year ago, said it was normal. I know it's not. I'm having them look at it again. If it happens, it happens at the exact same time the ICE engages, no other times.

Anyone have the issue?
It's the engine backfiring; it happens to most Gen 2 owners. Despite how ridiculous it sounds, it is "completely normal".

Half the Gen 2 owners on the forum are waiting for GM to find a fix for it but they don't seem too motivated to do so. I use my ICE every day and it does this almost every time it starts.
 
#3 ·
Could it be engine knocking?

If so, try better gas (or higher octane)
 
#4 · (Edited)
miamialley, SharkVolt, you can see what I think is the same problem in this thread:

http://gm-volt.com/forum/showthread...ming-from-rear-passenger-side-2016-Chevy-Volt

OP from that thread uploaded a Vimeo video that perfectly catches multiple instances of this issue. I'm still having it but haven't found the time during recent warmer temps (along with time off) to bring it to the dealer. Nearest Volt Techs for me only work weekdays so makes it hard to drop off and go for test drives.

I think in Arcanox's case, temperature was not a factor but in my case, whenever outside temp fell below 40F, I never had the backfire sound. Once above 50F, always have it. Inbetween, depends on how hot the engine becomes and how hard I accelerate. I've tried variety of gas from Fred Meyer (Kroger), Safeway, Chevron, Shell, and 76 to no success. I've only tried each once side from Safeway as I only fillup once about every month.

I also thought my recent oil change and recall for updating the "motor power inverter module" fixed things, but alas, temps were 45F that day so I was mostly getting no backfire until the engine finally warmed up to 190F.

Other users who may be experiencing this same problem:

http://gm-volt.com/forum/showthread.php?261057-16-Volt-backfiring
http://gm-volt.com/forum/showthread.php?227073-Clank-noise-when-on-ICE-and-making-right-turn
 
#7 ·
https://vimeo.com/177954038

WOW! I had missed those earlier threads.

How in the F does GM have the balls to say that this is "normal"?

Is there any indication that this has been fixed in newer vehicles?
 
#17 · (Edited)
I'll look into it. I thought this type of fuel is typically found at marinas where boats typically need 100% gas.

After reading this post and earlier related posts about this exhaust noise problem, all of the posters but one, are from CARB compliant States. Just to ask, is this issue mainly with CARB volts. Are the emission standards drastically different with the nonCARB volts?
Huh, this could be it. I don't recall seeing the T-ZEV package that Hornskeith mentioned, but plugging my full VIN # in I noticed that it has the "Emissions, Federal Tier 3" listed. I used the VIN decoder from chevroletforum.com/forum/vindecoder.php and went to the "Equipment" tab.

If this were the case, is there no way we can have the T-ZEV package removed or tweaked? I find it hard to believe that other vehicles with a T-ZEV package have a backfire sound.

EDIT: Just checked a listing for a Volt here in Washington and noticed the Volt has following options installed:

California ULEV125 Emissions Requirements
Northeast Emissions Requirements (Includes Connecticut, Delaware, Maine, Maryland, Massachusetts, New Jersey, New York, Oregon, Pennsylvania, Rhode Island, Vermont and Washington state requirements.)

We should start a poll about this with options like: a) my CARB Volt backfires b) my CARB Volt runs fine c) my NON-CARB Volt backfires d) my NON-CARB Volt runs fine.
 
#6 ·
Had my 2016 since 12/2016 and have experienced this issue ever since.
If it is a metallic "clank", then have the exhaust system inspected for loose or broken hangers or brackets. An engine backfire should not sound like a clank. Ask a volunteer to listen to the sound correctly (or better, record it) when it happens and to observe the tailpipe. If the pipe moves, then it is a mechanical issue.
 
#12 ·
Do you think the sound in the other thread:

http://gm-volt.com/forum/showthread...ming-from-rear-passenger-side-2016-Chevy-Volt

is metallic? Cause mine sounds exactly like that. If it is mechanical, how come during the winter with temps below 40F I can never get the sound again no matter how long I run on gas (both in HOLD and CS mode) and how hot the ICE gets <40F ambient? Wouldn't a mechanical issue still be present during cold temperatures? Just today it was 56F outside and I could get the backfire to sound almost 75% of the time.
 
#8 ·
You guys should be happy it sounds like a Audi RS with DSG transmission upshift pops. Just kidding.

The other day my car's maintenance mode kicked in for the first time...a month into ownership. You can really feel that engine kick in....it's not as smooth as one claims it to be and man...it really makes you appreciate EV's more.
 
#11 ·
My 2011 Volt with 92,000 miles, when the battery charge runs to minimum and the ICE starts, you hardly even know it's on. This is making me rethink my desire to purchase a Gen 2 Volt! How rampant is this problem? One definitely cannot put up with an engine backfire! Unacceptable under any circumstance.
I have mixed experience with the ICE. When cruising at a steady speed of 60MPH and I notice the energy consumption is below 15kW, the transition to ICE is pretty smooth. You can still feel it, only once did I not feel it at all and was surprised to start hearing the ICE. If consumption is above 15kW (e.g., you're going up hill even at constant 60MPH), then I can feel the ICE transition jerk my Volt. When I cruise at 30-40MPH, the energy consumption has to be below 7kW for a smooth ICE transition, other wise I feel a jerk. I plan on complaining soon when it gets really hot. I'm hoping to get a Volt or Bolt loaner (even if the Bolt seats are thinner, which I can confirm they are) during spring. I really don't want an ICE loaner but this is likely what they'll give me. This is the only thing deterring me from taking it in for fear the shop may try to diagnose the issue even though they know it's normal to backfire. I don't want to go back to driving an ICE.

miamialley, I too got the same response and was urged to take it up with my dealer if I really felt it was an issue. In other words, it might be just a waste of time.
 
#9 ·
My 2011 Volt with 92,000 miles, when the battery charge runs to minimum and the ICE starts, you hardly even know it's on. This is making me rethink my desire to purchase a Gen 2 Volt! How rampant is this problem? One definitely cannot put up with an engine backfire! Unacceptable under any circumstance.
 
#30 · (Edited)
I hadn't even heard of this problem until I checked in on the forum today after an absence of a few months, though admittedly, I haven't put as many miles on my car as some here. I've had my non-CARB '17 Volt for about 13 months now. It has just under 12,000 miles on it and has operated in EV mode 94.6% so far. Though the engine hasn't run that much, it has operated in every conceivable ambient condition at full operating temperature. It has never "chuggled" or made any weird noises or vibrations of any kind at any time. ICE operation (start/stop/engage/disengage) is very smooth and refined at all times. It's just excellent. Remember, people who are happy with their cars won't tend to appear here nearly as often as people who are looking for solutions to perceived problems. You won't regret the purchase of a Gen 2.



More accurately, if combustion occurs due to un-burned fuel or hydrocarbon igniting in the exhaust system this is an afterfire. A back-fire is when un-burned fuel moves back into the air/fuel intake system and combusts, this can be due to the intake valve or valves not fully closing prior to the spark igniting the fuel/air mixture in the cylinder.
I was thinking the same thing throughout this whole thread: this is not a backfire. You haven't lived until you've lost eyebrows to fire belching from a Holley carburetor...that's a backfire! Ah, the good old days...



The ICE in the Volt achieves its Atkinson Cycle-style operation, not through dynamic changes to the mechanical length of its crank stroke (as in the original, complex Atkinson design), but through intentional wide variations in cam phasing...which achieves most of the same effect. Hey...wide variations in cam phasing...couldn't that mimic the effects of a worn out cam chain, if it was carried a bit too far under just the right circumstances? Only, in this instance, allowing combustion gasses to leak downstream into the exhaust? They might do this purposely...perhaps to keep the cat warm or to warm it more quickly. Hmmm...
 
#10 · (Edited)
I got this private message as a response to this thread today:

"We came across your post on the forum, and though we recognize you're seeking advice from other users, we did want to weigh in with the information we have from our end as well. Our internal technical resources here at GM have advised us that this is in fact considered to be a normal operating characteristic. We understand this isn't the answer you were hoping for, but we wanted to reassure you that your Volt is considered to be operating as normal.

If you have any questions or concerns, please feel free to let us know."

Kindly,
Lauren E.
Chevrolet Customer Care
 
#13 ·
After reading this post and earlier related posts about this exhaust noise problem, all of the posters but one, are from CARB compliant States. Just to ask, is this issue mainly with CARB volts. Are the emission standards drastically different with the nonCARB volts?
 
#14 ·
All the cars listed on dealership sites from CARB states list Low Emissions Package (T-ZEV) in their options list, so it's at least possible. But lots of Volts are also sold in CARB states due to the incentives.

FWIW, my non-CARB Virginia Volt doesn't have this behavior, but it was also built last December.

Keith
 
#20 · (Edited)
Got a response back from Chevy via this forum:

"Thanks for your patience as we looked into this further. Unfortunately, we're unable to speculate as to why all Volts don't experience the noise. This is because there are many usage factors to be considered that might cause some drivers to observe the noise, while others do not.

We apologize in advance for not being able to provide additional insight on this. However, we want to again reassure you that this is nothing out of the ordinary, as the noise is considered to be a normal characteristic. If you have any additional questions, please let us know."

___

So, they say it's normal, but won't say what it is or why it does it.
 
#21 ·
I'm still not convinced this is normal. It may be harmless, and it might be "normal", but it's definitely not normal for an ICE to backfire when starting up. No other hybrid I have driven or seen does this but the Gen2 Volt :mad:

The noise being normal also doesn't make it not annoying...it's kinda awkward driving friends around being like "listen to how quiet my car is" only to be followed by "poPOPOP" when I accelerate.
 
#24 ·
#25 ·
I do not believe I have ever experienced this in my 2017 Volt with 8k miles, 90% EV driving. On longer trips I will engage Hold mode when driving on the highway at 50mph or greater speed.

Based on the video and eye witness accounts the source of the sound appears to be momentary after burn in the exhaust stream. This is most likely due to incomplete combustion of fuel during startup of the ICE. If GM is aware and states that this is normal for the Gen II Volt, not a problem, then should a problem develop with the exhaust system or catalytic converter GM should make any necessary repairs. The exhaust system and catalytic converter would be covered under the 8yr/100,000 mile drive train warranty that includes fuel system and emission controls.

This my be off topic but I definitely sense that GM, other manufacturers, are shifting their automotive designs to a shorter life span. Cars and trucks may not rust like they used to do but other materials, technology including software will make it very difficult to keep our vehicles running for as many years as we have in the past. It is going to be hard to keep current production vehicles on the road for more than 10 years, technology and safety and environmental regulations are changing too fast.
 
#26 ·
I do not believe I have ever experienced this in my 2017 Volt with 8k miles, 90% EV driving. On longer trips I will engage Hold mode when driving on the highway at 50mph or greater speed.
You won't notice it unless you run the engine until the coolant reaches ~190 *F and then drive in stop/go traffic. Almost every time it starts hot, it'll produce this noise, but you won't really hear it at higher speeds because the engine remains on almost 100% of the time and road noise will drown out the pop noise.
 
#27 ·
Adding another scenario to Arcanox's info, even with coolant at 190 degF, I no longer had the backfire during ambients of 40 degF or lower. Arcanox, I recall, had it no matter the ambient. This all appears to play into the incomplete combustion theory (backfire).
 
#28 ·
More accurately, if combustion occurs due to un-burned fuel or hydrocarbon igniting in the exhaust system this is an afterfire. A back-fire is when un-burned fuel moves back into the air/fuel intake system and combusts, this can be due to the intake valve or valves not fully closing prior to the spark igniting the fuel/air mixture in the cylinder.
 
#34 ·
Did a lot of driving this weekend (RIP MPG) And heard the thunk once during fairly light acceleration. Change my vote to Yes :(

It wasn't loud and no one outside of the car seemed to have noticed it but I did so GRRR!

It has nothing to do with CARB. My car was built with Georgia as the destination in mind.
 
#36 ·
We can't really tell because it happens from the start of ownership (or at least the start of ICE usage).

It's really annoying and attention-grabbing regardless...
 
#37 ·
I've still got like 1/2 a tank left of ethanol+gas blend, but was hoping to try 100% gas by using a marina gas station. I don't understand how it might affect things, but it's simple enough for me to try and I need gas anyway. I'm hoping maybe it'll change the behavior.

I'm also wondering if winter vs summer blend of gas has an effect. I can't recall when I first heard it relative to the winter vs summer gas blend change.
 
#38 ·
For some reason this thread wouldn't let me vote, but my 2016 Volt does this too. It's very embarrassing when taking friends and family on rides to "show off" the car and have a loud bang noise happen when the engine comes on! Why is GM not fixing this??? This is not "normal"! Do the other 20 hybrids out there do this (I don't know if there are 20 but it sounds good)?? NO! So by dictionary definition this is "abnormal"! HELLO GM, ARE YOU LISTENING!? I want this fixed. Put those over-priced engineers of yours to work, come up with a solution, and fix everyone's car that they just paid you $30,000 for.
 
#39 ·
Oh thank God I'm not crazy. My 2017 has been doing this since 500 miles. I've taken it into the service center 3 times now and they can't figure it out. They even replaced the rear axel thinking that was the problem. Last week I finally figured out it happened more often when it switched from electric to gas and was going to take it back to service with this new information. I guess that is a waste of time though after reading this thread and the other one. Such an annoying issue.
 
#40 ·
Yeah, it's real annoying. I'm still on 3 bars of gasoline (great weather, 100% EV commute 1/2 of the time) and still haven't switched too pure gas. Though, if it's pure gas, I would expect the exhaust would be even richer and cause more after fires.

Now that weather is warmer consistently, I may just force myself to burn gas so I can bring it to the dealer and show them.

Thing is, I really hate being without my Volt. Makes the commute so much better.
 
#41 ·
Though, if it's pure gas, I would expect the exhaust would be even richer and cause more after fires.
You mean instead of E10? I'm curious to know if it would change the behavior at all...I don't know where I'd get pure ethanol-free gasoline here though. I have noticed recently that if the engine starts up to a low RPM, it's far less likely to afterfire. Usually I accelerate at about 45-50 kW on the meter, so when the engine fires up, it immediately revs up. Lately I've been getting behind extremely slow drivers so I'll barely have my foot on the gas, and by the time the engine starts I'm barely moving, so it starts but remains nearly idling, and in that case I've never noticed an afterfire.
 
#44 ·
Yes -- I get the occasional clank as well. Sounds like a flap in the exhaust system that's closing or something. Mine happens after the ICE has been warmed up and driven on for a period of time. Usually hear the clank right when I'm accelerating from a dead stop. Mine's a 2016 Volt LT, Oct. 2015 build date, California car, 28,000 total miles, about 7,000 ICE miles.
 
#45 · (Edited)
So I filled up my tank from 1.6 gal of gas+ethanol (I forget the %, but I think 10% is safe to assume) to 8.9 gal of pure gas. Given similar ambients so far (50F morning commute on ICE, 60F-75F evenings on ICE) I think I'm getting more afterfires now. I used to only get a single bang, but now I occasionally get 2 in a row from a single acceleration. I do not think I let off accelerator then re-apply accelerator, just a single, smooth acceleration. I purposely skipped an overnight charge to do morning and evening commute in CS mode. I only tested in HOLD mode during my evening commutes but will test again tomorrow.

It's now annoying me. I prefer the single afterfire when on ~E10 gas. Seems to me the fuel mixture is getting more rich? I thought modern ICE engines have various sensors that prevent oddities like knocking and misfires.
 
#46 ·
Dang you were only getting one pop before? I usually get 2, sometimes 3 or even 4 on a "good" day. I guess I shouldn't put pure gas in it then :p

I wonder if I could find a place that sells E15 instead of E10 and see if it has the opposite effect...
 
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