What color was the smoke? https://www.freeasestudyguides.com/exhaust-color.html

 

It was predominantly white smoke, but I think I saw some brown in there.

I was unsure if it was smoke or steam...

 

That does not sound normal. Usually smoke or steam from the back means something is really wrong and fluids are passing into the wrong place due to a blown gasket or seal. It is a good sign that your fluid levels are normal. Keep an eye on them. Maybe if you are lucky, it was a freak thing where some road debris got onto the outside of a hot exhaust part and burned off.

 

So far it is a one-time event. The rest of the drive that day I saw no smoke and I went 100 miles and had a couple more steep climbs. Two days later I drove 120 more miles on gas and no smoke.

The dealer was unable to reproduce the problem and he ran quite a few test miles. He checked out the cooling system for leaks as well.

There is the possibility some cooling fluids ended up where they weren't supposed to be. Perhaps an overflow. Conditions were about as extreme as they could be, with the high temp, running the AC and accelerating heavily from 25 to 55 on a 6% uphill grade.

 

I've never heard of a blown head gasket or a warped head healing itself.

 

This was where I was perplexed. Most of the things that white smoke indicate are not self healing. They would be ongoing.

So what would cause a one-time smoking event that did not continue just 10 minutes later after I went back to mountain mode and the engine turned back on?

 

Definitely check the oil for "pudding"
https://discourse-cdn-sjc1.com/cart...talk/uploads/default/original/2X/5/5ec6f478dac5dcc83d84c462373b84344b5616e0.jpg

 

Oil was at 25% at the time. When I had it at the dealer to be checked out after this event, I had him do an oil change...

 

Condensation in the exhaust? This was a common issue in my old Saab, but only right after startup in certain environmental conditions.

AC condensation pooling somewhere under the hood and then hitting the exhaust once you floored it?

 

AC was working hard so there was sure to be a lot of condensation. Maybe some condensation from the AC hit the engine block or exhaust...

 

Which brings up an interesting question. How does the car determine "oil life"? Would sudden water in the oil zoom it to "end of life" reading?

 

It doesn't actually measure anything about the oil, just informed decision based on operating parameters
e.g. operating/ambient temp, engine on duration, sustained and instantaneous load/rpm, etc.
So a catastrophic failure that injected water into the oil would not be detected.
The resultant change to engine parameters would though, e.g. overheating

 

THE BLESSING IN ALL THIS

That I had the option to switch to normal and climb the rest of the hill on electric.

If I was in an ICE vehicle and it started smoking, there is no way I would have been able to finish climbing the hill. I would have had to pull over.

 

I wasn't able to get a straight answer from the dealer about what it really was. I didn't feel he did as thorough a job of troubleshooting as I would have liked. Mostly what he did was a lot of test driving and looking for smoke. He found none. His finally analysis was "CANNOT REPRODUCE PROBLEM".

I didn't have the tech do the oil change until after he was done testing, so the oil condition was the same during troubleshooting as it was when the incident occurred...

I suspect that I won't know what happened unless it happens again, which sucks. I would have preferred to have a more definitive answer, but the dealer did not provide one...

 

I would go with it being an over rich fuel situation due to the heat and the sudden acceleration while in mountain mode. Grey brown smoke usually would indicate a fuel issue. Other possibility is that a bit of oil blow by on the piston rings. Perhaps you had a piston ring that was not quite free and it is now due to the extremes of the sudden acceleration and resulting high revs. At any rate, if it was something worse you would have other things showing up such as coolant in the oil or oil in the coolant, ongoing smoke or noises or CEL.

 

I am hoping along these lines being I drove another 250 miles on the engine over the next 3 days, with multiple hill climbs, with no smoke.

 

Perhaps there was an excess amount of moisture buildup in the CAT that got hot enough due to the sudden load you put on the engine and that turned to steam and a mixture of other carbon deposits that came out as "dirty smoke".
But I would be keeping a close eye on all fluid levels and checking the oil for any discoloration just to be safe.

 

This seems quite plausible given the sudden Demand on the Cold engine.
If you’re in any kind Mountain driving the car should be in Mountain mode before you need it. If you fall below the mountain mode hold line and then suddenly ask it for help it’s going too race too maximum rpm in an effort to not only sustain battery level but also charge it.

I am curious how much regen was gained on that 5 mile decent to Verde Valley? I’ve driven that once in a rental car and had too keep it down shifted things under reasonable speed control.


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Did I miss the answer to whether Regular or Premium gasoline is being used?

 

Nothing but premium for the entire life of the vehicle...

 

Was there any smell associated with the smoke? If so, it's usually an easy way to tell the difference between burning oil and burning coolant.

 

It happened too quick for me to notice a smell....

The more I think about it, the more I think the smoke was more black than white, which would indicate a fuel issue more than an overheating issue.

 

How about maybe you cremated a squirrel nest under one of the plastic covers.

 

Did the smoke appear to be coming from the exhaust pipe, or was it possible it was coming from somewhere else?
If you got a lot of white smoke, and it wasn't the exhaust, you could have caused the radiator to bleed off some steam. Trapped water from the AC condenser wouldn't make much smoke, because there's really no way it could collect enough.

If you think it was more gray and coming from the tail pipe, then that would definitely point to unburned fuel. In the high elevation, your oxygen levels are already lower. Add in the extreme heat and sudden change in throttle input and the engine was probably feeding way too much fuel.

 

I only saw it in the rear view mirror, so that leads me to believe it was coming from the exhaust.

The Phoenix to Flagstaff climb goes from 600 feet to 7000 feet. I was at about 4000 feet when it occurred.

The more input I get from you guys, the more I am feeling it was a one time excessive unburned fuel situation. That is the best case scenario without a doubt.

Since no other Volt owners have reported anything similar, it sounds like it was a one-off situation that is unlikely to occur, if I show a little more respect for the hills....

Thanks for all the input everyone. Feeling relieved....

 

Since this thread already has a lot of different theories, I will add 2 more possibilities-
1 any rain recently, or washed the car recently , that there might have been water puddled in the air intake somewhere that just needed the right combination of hill and air volume flowing past it, and acceleration, to get it up into the airflow?
2 perhaps some oil had accumulated in the pcv to manifold tubing and the extra air flow from the high rpm, open throttle operation was enough to push it into the manifold. I know that shouldn't produce white smoke, but you were looking in your rear view mirror while driving, so I'm willing to discount the smoke color a bit.
good luck.

 

I had this problem as well in the same situation. I use the engine maybe once every 3 months during the summer. I was going up I70 / hill climb and put the car in mountain mode. It was into high-revs to recover and suddenly I had some black smoke coming out. Within a few seconds the check engine light starting blinking as well. I pulled over to the side of the road and turned off the car - and the smoke stopped and the check engine light was no longer on after I restarted. I went back down the hill and aborted by trip although the engine had to come on again due to mileage - but no smoke.

The dealer found no issues. Not even the blinking check engine light apparently threw a code that they could recover. From what i can tell this is a catalytic converter overheat warning though.

This happened a few years back and I've since done the same hill climb in the same mode with no issues. 10's of thousands of miles with no more issue.

So here's my theory. After months of sitting outside while at work, something decided to build a nest somewhere in my exhaust system. Spiders, or who knows what. Whatever it was got roasted due to the "clean" mode that mountain mode initiated and now we're all good.

From the discussion so far, sounds as reasonable as the rest of the guesses.

TLDR - mountain mode acts like an oven cleaning mode for exhaust systems!

 

I didn’t use mountain mode or have smoke that I noticed. However, occasionally I get the “engine under reduced propulsion” warning after turning the car on with a depleted battery and if I drive it right away, the engine races. I think it is burning oil because of the high rpm’s. I smell a burnt oil/rubber smell from under the hood. To avoid this, i let the engine idle for anywhere from 3-5 minutes until it shuts off. I presume the battery went below the 20% charge threshold somehow and needed to get back up to that before running under normal power. So my non-professional 2 cents is that some oil burns due to the high rpm’s.

 

Yeah, for the brief period that I had the PPR issue I also noticed that the car would smell like burning oil after it had been racing to recover the battery buffer. My only guess was that the high RPM was pulling oil through the PCV system and burning it.

As an aside, there is a software fix for the PPR issue, though you'll likely lose 10% usable battery.

 

If you google "bird nest in tail pipe" you can find discussions about that being an actual problem for some people. I think especially RV owners, maybe because the vehicles sit parked for long periods. The Volt tail pipe is rather narrow, so may be less attractive to most birds, but other things might nest in there. I could see something like that causing temporary smoke.

 

I'd venture to guess the ecu was commanding extra fuel to keep the crowns of the pistons cool.we do that regularly in marine superchargered engines and most endurance engines,drag race not so much.

 

Maybe it's just "blowing the carbon out"

 

IMO, if your head gasket had blown, you would have noticed a change in the sound of the engine and the gasket would not have healed itself.


Driving back from the Finger Lake Region of New York in my TR-7 thirty some years ago, I blew a head gasket when I was half way between Monticello and Liberty on Rt. 17. I first noticed it when the sound of the engine changed. I glanced up in my rear view mirror and saw the white smoky exhaust billowing out behind me. The car had about 110,000 miles on it at the time.


After jogging 5 miles to Liberty to catch the last bus to NYC (just making it), I was able to catch the last train to Huntington…got home at 3:30 AM. Went back the next day with my brother-in-law and towed the car home. After replacing the head gasket (after checking the cylinders for scoring) and following the unusual torqueing pattern for the head bolts, I drove it for another 20,000 miles.


That was a fun car to drive. The Volt is also a fun car to drive. Enjoy yours for many years to come. I'll be doing the same

 

Hold the phone everybody. The answer was in the 3rd paragraph. A/C was on the whole trip. Climbed hill with engine on. The smoke was the a/c high pressure popoff valve. When this happens it creates a huge cloud of smoke and if any hits the exhaust the cloud gets even bigger. Several reasons for this. Hot day in Arizona long trip ac on, could have just reached critical mass. Could have airflow problems i.e. Air dam damage. Could have debris in between radiator and condenser. Doubt it but the ac may have been overcharged (I have never charged my 13). Jumping to blown head gasket and rodents in the exhaust is a little crazy. Head gaskets don't get better, rodent would be gone a few seconds after engine start. Evaporator condensation is specifically routed away from anything hot. I'm surprised the mechanic that checked it out didn't come to the answer immediately. If the ac is working I would just leave it alone. Sorry I didn't see this earlier, would have saved you some stress.

 

Good suggestion that maybe the AC experienced an over pressure condition. The op did state that the smoke coming from the rear of the Volt (not from under the hood) stopped as soon as they switched to Normal mode from Mountain mode for the remaining 1 mile of the hill ascent where the smoke started appearing. It's not the rodent which would probably skedaddle as soon as the vehicle started but the nesting material and food supply the rodent leaves behind.