# Cloud of blue/white exhaust smoke



## MP81 (Jul 20, 2015)

I have never once seen smoke out of ours (granted, it is a 1st gen)...is this the first time this has done it?


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## Barry Allen (Apr 18, 2018)

MP81 said:


> I have never once seen smoke out of ours (granted, it is a 1st gen)...is this the first time this has done it?


From what I know, yes, this would be the first time. Within about a half mile of flooring it to see if the smoke was still there, it appeared to clear up and disappear.


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## TDCruze (Sep 26, 2014)

With the cold there is definitely more steam from the moisture in the exhaust forming a white cloud. Shouldn't be any dark smoke due to the DPF catching almost all particulates. May have been extra moisture in exhaust from idling so long?


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## Barry Allen (Apr 18, 2018)

TDCruze said:


> With the cold there is definitely more steam from the moisture in the exhaust forming a white cloud. Shouldn't be any dark smoke due to the DPF catching almost all particulates. May have been extra moisture in exhaust from idling so long?


It was more than moisture. It was definitely smoke, and it had a blue tint.


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## Phalanx (Oct 28, 2017)

thats from oil getting combusted. engine was probably still cold so you had some blow by or turbo seals.


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## JLL (Sep 12, 2017)

To my knowledge it's not normal for any engine to burn enough oil to see smoke out of the tailpipe.


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## Barry Allen (Apr 18, 2018)

Phalanx said:


> thats from oil getting combusted. engine was probably still cold so you had some blow by or turbo seals.


Wouldn't the DPF trap any smoke?

The engine wasn't at maximum normal temperature, but it was warmed up while idling.


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## Barry Allen (Apr 18, 2018)

JLL said:


> To my knowledge it's not normal for any engine to burn enough oil to see smoke out of the tailpipe.


The only car I had that would do this was my RX-7, but that car was consuming a quart of oil for every tank of fuel.


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## Phalanx (Oct 28, 2017)

it should but i guess it didnt. probably means there was that much more smoke then what you actually saw.

i would keep an eye on it. it can be so many different things but oil getting in the CC makes blueish white smoke.


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## JLL (Sep 12, 2017)

Barry Allen said:


> The only car I had that would do this was my RX-7, but that car was consuming a quart of oil for every tank of fuel.


That's got a Wankel rotary engine in it. Oil consumption is normal in those.


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## TDCruze (Sep 26, 2014)

Barry Allen said:


> Wouldn't the DPF trap any smoke?
> 
> The engine wasn't at maximum normal temperature, but it was warmed up while idling.


Yes, that is what the point of my first post was. There should not be any blue smoke due to the DPF capturing it. If there was blue smoke then there would have to be a lot of oil saturation in the DPF. That is not normal.


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## Barry Allen (Apr 18, 2018)

JLL said:


> That's got a Wankel rotary engine in it. Oil consumption is normal in those.


Oh, I'm aware. Mine was especially worn out before it finally quit.


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## Barry Allen (Apr 18, 2018)

TDCruze said:


> There should not be any blue smoke due to the DPF capturing it. If there was blue smoke then there would have to be a lot of oil saturation in the DPF. That is not normal.


I was somewhat alarmed at it. 

When the smoke cleared up I noticed it was doing a regen cycle and I parked the car before it was completed.

Tomorrow will be another very cold day but I will be doing highway driving, so the car will be thoroughly warmed up at some point. I'll keep an eye on it and see what happens.


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## TDCruze (Sep 26, 2014)

Definitely continue to monitor it, and spend a good 20-30 minutes on the highway tomorrow if you can to burn if all off. Keep an eye on engine oil level and for unusual fuel consumption rates.


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## Carminooch (Mar 23, 2018)

My 2018 diesel puffs out a little blue/grey haze on first startup. I noticed it at 10,000 miles. It’s so faint but when it’s cold, it’s especially a little more pronounced. 

I’ve never seen any on acceleration though. Two guesses:

1) the car was idling and while warm, wasn’t fully warmed up, and unburnt hydrocarbons accumulated in the DPF that you kicked out when you took off on the highway
2) I had a scare where I was in front of a G class with those new stock blue HID/LED headlights. I was stopped at a light, cold day lots of humidity, the cars lights behind me made the excessive steam my car was emitting look like blue burnt oil.


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## MRO1791 (Sep 2, 2016)

It certainly doesn't seem normal. White smoke can be fuel dumped post combustion in the exhaust, but the DPF should be using this during a regen, since you indicated a Regen about this time, it's possible the car was trying to regen, but could not attain the light off temperature, and thus the unburned fuel built up.. BUT the DPF should not normally let the smoke get by... that part is confusing.. unless you have a damaged DPF that is letting unfiltered exhaust pass through, and that is a real possibility, it does happen.


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## Snipesy (Dec 7, 2015)

While cold most white and bluish smoke will be a mix of water vapor and unburned raw fuel. Basically diesel vapor. Not the same as soot and doesn't stick in the dpf like soot.


So when you accelerate it all gets pushed out. Hence the plume.

The ubnurned fuel is mostly harmless minus a potential fire hazard. However its a sign of a cold cat so NOx and CO levels will be high in the exhaust. Hence the smell. But the smelly stuff is actually invisible.


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## Snipesy (Dec 7, 2015)

Also to go on further all diesels will be aggressive at heating up the cat. They forego some emission requirements in exchange for getting the catalyst in working order quickly. This 'rapid heat up' nets less emission in the long run.

So yes the plume can be removed with a proper tune but its generally not advisable. Even in deleted cat less applications.


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## Barry Allen (Apr 18, 2018)

Snipesy said:


> Also to go on further all diesels will be aggressive at heating up the cat. They forego some emission requirements in exchange for getting the catalyst in working order quickly.


I've noticed this on my car. On any given cold start (even in warm weather) I will be driving to work, have the cruise control set at 35 mph on my way to work, and my fuel economy will hover at around 30 mpg. It's the car warming up the catalytic converter by dumping extra fuel into the exhaust stroke. On warm days I'll see this happen for a mile or two, but on really cold days (like this morning) it stayed at about 30 mpg all the way until I parked at work. Then it did the same on my drive home.


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## MP81 (Jul 20, 2015)

Yup - makes sense. Gas cars do that, as well. 

I wonder if tunes that delete the cat stops the engine from doing that...hmm...

Not that it matters for me, I still have a (high-flow) catted downpipe in the Cobalt. The Camaro doesn't have a cat anymore, but I'm pretty sure that wasn't "programmed" into the ECM in 1981 anyway.


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## Barry Allen (Apr 18, 2018)

MP81 said:


> I wonder if tunes that delete the cat stops the engine from doing that...hmm...


My understanding is that on a very cold start, you have to have enough exhaust heat to keep the water vapor from plugging the DPF. You have to have it flowing through there at high temperatures, quickly, so it doesn't freeze up the DPF and cause restrictions.

If you physically removed the DPF, you could easily tune it to not matter. If you left the DPF in place, the aftermarket tune should probably be mindful of the exhaust temperatures to keep it from freezing up.


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## MP81 (Jul 20, 2015)

I was speaking more for gas engines, going off topic, haha.

Yeah, I don't expect the Trifecta tune on our CTD would change any of that.


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## TDCruze (Sep 26, 2014)

The DPF definitely lights off fast on the gen 2 diesel. It can resume an interupted regen on a cold engine quite quickly.


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## Snipesy (Dec 7, 2015)

Barry Allen said:


> I've noticed this on my car. On any given cold start (even in warm weather) I will be driving to work, have the cruise control set at 35 mph on my way to work, and my fuel economy will hover at around 30 mpg. It's the car warming up the catalytic converter by dumping extra fuel into the exhaust stroke. On warm days I'll see this happen for a mile or two, but on really cold days (like this morning) it stayed at about 30 mpg all the way until I parked at work. Then it did the same on my drive home.


Yeah. It can take up to 10 to minutes if it’s super cold in my experience. While driving. Idling can be a bit finnicky.

On the Gen 1 the warm up stages were usually done shorty after the ECT needle starts to move. Unfortunately there is no pid that tells us this because GM loves us.


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## Barry Allen (Apr 18, 2018)

Today, with the long drive, there wasn't anything unusual going on. The car didn't have any smoke at any point. I did find it interesting that it went through three separate regen cycles. The regen from yesterday was never completed so when I was leaving town it was warming up and doing a regen cycle for at least 15 miles. Then, when I was driving slower to come into a city south of me, it went through another mini-regen cycle. Lastly, as I was approaching my parents' house after driving across the city, it was in regen again for a few miles.


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## Barry Allen (Apr 18, 2018)

Snipesy said:


> Idling can be a bit finnicky.


At the fuel stop yesterday, the engine was just coming to be a bit warm. I left it running with the interior fan on high just to get some heat into the cabin while I was pumping and paying. I'm going to assume the engine was doing some wet stacking where cold temperatures in the cylinder combined with low pressure meant the fuel wasn't completely combusting and was probably wetting the inside of the exhaust system. Some medium intensity pulls when going onto the highway blew all the smoke out of the exhaust for about a mile or so.


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## Cruz15 (Mar 17, 2016)

Both my Gen 1 and Gen 2 did the mini regen cycles which were noticeable. Only my Gen 1 did the blue smoke thing, the dealer didnt know why or how. Snipesy probably knows more about issue than the GM techs.


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## Barry Allen (Apr 18, 2018)

Cruz15 said:


> Both my Gen 1 and Gen 2 did the mini regen cycles which were noticeable.


It's the first time I've seen it, but it's during very cold weather. I'm guessing the low speed driving when I was loafing across town wasn't making high enough combustion pressure/temperature for a clean burn inside the cylinders and it was loading up the DPF.

Run a diesel engine at higher speeds with a decent load and you get high boost pressure from the turbocharger that really cleans up the exhaust. There are a number of diesel engines where an added turbocharger doesn't increase power much (International-Harvester 6.9 and 7.3 IDI engines, looking at you) but it really does clean up the exhaust. I know a farmer who owns an army surplus deuce-and-a-half, and the history of that engine was similar: the turbocharged version is only 5 more HP, but a lot less black smoke out of the stack.

Winter fuel also drops some cetane with more refining to get the cloud point lower. I'll pour some cetane booster in the tank tomorrow and see if that helps.


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## Snipesy (Dec 7, 2015)

Cruz15 said:


> Both my Gen 1 and Gen 2 did the mini regen cycles which were noticeable. Only my Gen 1 did the blue smoke thing, the dealer didnt know why or how. Snipesy probably knows more about issue than the GM techs.


GM doesn’t publish any of this information.


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## Barry Allen (Apr 18, 2018)

Snipesy said:


> Idling can be a bit finnicky.


When I was a kid there were a handful of people who owned Ford pickups with the 6.9 IDI engine. Those people were the handful of Diesel "wizards" who dispensed advice that you could never tell if it was witchcraft or actual good practice.

One guy seemed to be a professional at having his truck running at peak performance, because he used it for actual work in a real business. He did three things:
1. A real serious engine block heater was always plugged in when he was home. It was plugged in for probably 4 months out of the year, because the engine was cranky to start at temperatures lower than about 50ºF.
2. He had replaced the glow plugs in his engine with some "marine duty" glow plugs that were something special to where they could be left on for long periods of time. He had a manual switch in the cab to turn the glow plugs on and he would have them on when the truck was idling or doing anything at low speeds in cold weather. When he was doing highway driving and the engine was up to temperature, he'd turn them off because it was not necessary at that point.
3. He had an ether injection system for really cold starts. With glow plugs disabled (that manual switch turned off) he would crank until there was white smoke coming out of the exhaust pipe. Then, a small blip of ether into the intake, wait about 10 seconds for it to vaporize, and the truck fired up after about 2 revolutions of the crankshaft. Once it was running he'd then turn the glow plugs on to clear up the white smoke in the exhaust until the engine was up to temperature.

That guy never had any problems with his truck and it never failed to start when he had to do a really cold start if the truck was parked somewhere without access to plug in the block heater. The truck cleared 250,000 miles before he sold it when he upgraded to a Ford with the 7.3 Powerstroke engine, and he replicated the ether start system for use in that with a manual glow plug disable switch.


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## Jetmangler1 (Jan 20, 2021)

Barry Allen said:


> Are these cars known for leaving a good cloud of blue/white smoke on heavy acceleration?
> 
> Today was a cold snap (down to about 15ºF) and I was filling up with fuel. I left the car idling while filling the tank and paying just so I could crank the cabin heat and get some going. When leaving the fuel station, I did a couple hard accelerations onto the main highway through my city and in the rearview mirror I saw quite a bit of blue/white smoke. It wasn't anything like how pickups roll coal with the douche nozzles and their tuning boxes, but it was definitely a noticeable amount of smoke. The Porsche Macan following me from the stoplight pulled back from the smoke I was leaving
> 
> In cold weather, do these engines idle and leave excess fuel in the exhaust that then burns and smokes out of there when you pull away from a stop?


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## Barry Allen (Apr 18, 2018)

Jetmangler1 said:


> In cold weather, do these engines idle and leave excess fuel in the exhaust that then burns and smokes out of there when you pull away from a stop?


That's what I think happened. It surprised me with a modern diesel vehicle, but the weather conditions at the time make me believe that's possible for what I saw.


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## Cocodabney (Jan 16, 2021)

Barry Allen said:


> It was more than moisture. It was definitely smoke, and it had a blue tint.


I just got rid of my 2016 last week for this exact reason. Everyone I got to look at it said the engine was gone. The oil from the engine ended up pouring from the exhaust pipe. Causing it to smoke. One mechanic said it traveled through the gas line. Would’ve cost $6.000 to fix it because no one near me had the engine except the dealership. Sold it for $1000 and now it’s someone else’s headache.


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## Barry Allen (Apr 18, 2018)

Cocodabney said:


> I just got rid of my 2016 last week for this exact reason. Everyone I got to look at it said the engine was gone. The oil from the engine ended up pouring from the exhaust pipe. Causing it to smoke. One mechanic said it traveled through the gas line. Would’ve cost $6.000 to fix it because no one near me had the engine except the dealership. Sold it for $1000 and now it’s someone else’s headache.


How much oil consumption? I’ve owned a car that consumed a quart every 200 miles. For me, that meant I changed the filter every 3,000 miles and never changed the oil. Castrol 20W-50 was 89¢ a quart so I bought it by the case.


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## Barry Allen (Apr 18, 2018)

Today I noticed more smoke out of the exhaust. I was leaving work and the engine was barely warmed (the needle was off the lowest reading, so slightly warm) and I used some power to rush through a yellow light. There was another stream of bluish white smoke behind me and a coworker following me confirmed it wasn't just moisture from the exhaust.

It appears that the engine is using excess fuel to warm up the catalyst during cold running and when I use the accelerator with moderate enthusiasm, it's a cloud of blue smoke out the exhaust. Oil level in the crank is right at normal, so it's not excess oil being consumed that I can notice.


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## Barry Allen (Apr 18, 2018)

More blue smoke this afternoon while the outside temperature was in the low 30s F. I noticed the car was idling slightly rough, almost imperceptible, but the tach needle seems to fluctuate by about 50-100 RPM while at a stoplight, and I know that the engine is usually steady as can be with electronic injection control. After waiting at a stoplight for a couple minutes, I can pull away with moderate acceleration and get a huge blue cloud of smoke out of the exhaust.

Also, the car was running another warmup or regen cycle. I took it out for some highway speeds for about 10 miles and it still was in regen when I got home and parked. I can't tell if the blue smoke is because the car is running a regen and I'm giving it some acceleration, or if the blue smoke is the cause of the regen cycle (loading up the DPF).

Chevy dealership will look at it on Monday. I'll take it there and demonstrate what it's doing for them. Maybe it's got a bad injector that isn't throwing a CEL, or something similar.


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## MP81 (Jul 20, 2015)

It seems like it's doing it pretty consistently, so I fully expect it to fix itself on Monday rather than show the dealership something is wrong, haha.


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## Barry Allen (Apr 18, 2018)

MP81 said:


> It seems like it's doing it pretty consistently, so I fully expect it to fix itself on Monday rather than show the dealership something is wrong, haha.


That's a definite maybe. I'll drive it over there cold on Monday morning and I'm going to make the technician witness it while I'm driving it around the block. I'm not going to play that game of "We can't duplicate the problem."


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## MP81 (Jul 20, 2015)

We took ours in there for the ongoing transmission issues before the PT warranty was up, mainly for a hard point in the data, should something ever actually come of it, we've got a spot where we can say "Hey, we took it in with this issue here, when it was under warranty". Of course, they couldn't duplicate it.


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## grs1961 (Oct 23, 2012)

If you have a problem, and just drop your car off, then they won't diagnose it.

Take some time off work, and drive around with the service-type and demonstrate the problem to them, it's the only way.

Although, in this case, leave the car outside the dealer the night before, and get there some other way, so that you can take them out to a cold car and show them.


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## Barry Allen (Apr 18, 2018)

grs1961 said:


> Take some time off work, and drive around with the service-type and demonstrate the problem to them, it's the only way.


I'm going to have my sister's husband follow me tomorrow morning to take video of the smoke. On Monday morning, I'm going to wait at the dealership until the technician is available and I'm driving him on a short loop around the roads near the dealership. I already showed the service writer and he saw it himself, so they have one person there that knows this is an issue when he was writing up the ticket.


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## MP81 (Jul 20, 2015)

Oh that's good - so one person has seen it, and the video will be another piece of evidence.


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## Barry Allen (Apr 18, 2018)

MP81 said:


> Oh that's good - so one person has seen it, and the video will be another piece of evidence.


I'm going to make the technician witness it themself. I'll stand in their service department until the technician is ready for a quick ride-along. When you stand right in front of their service counter staring at them, the do things to try to get you to go away so I'm sure they'll pull the technician to go do this as quick as they can.


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## MP81 (Jul 20, 2015)

Absolutely - make them uncomfortable, and they'll look at it right then.


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## Barry Allen (Apr 18, 2018)

I got every customer's favorite answer: "UNABLE TO DUPLICATE ISSUE"

This issue first appeared on the 22nd, right after I fueled up the car. It continued basically every day of the week (Tuesday, Wednesday, Thursday, and then Friday) when the weather was cold and the car was trying to go through a regen cycle but could not complete it because of the cold weather and intermittent city driving. On Saturday I was leaving the McDonald's drive-thru onto the highway and I did a long, hard pull through 3rd gear up to about 80 mph and it was streaming smokescreen that would make James Bond jealous. Q would be proud. That highway driving did let the regen cycle complete after about 10 minutes and it was back to fuel economy in the high 40s (winter fuel, so under 50 mpg is typical).

The service writer did see the cloud of smoke that I was able to show him on Friday when I was setting up the appointment. The technician had the car on Monday and could not duplicate it in similar weather conditions. They even let the car cold soak overnight and the problem did not appear this morning. Their notes: ECM DATA INCLUDING, EGT SENSORS, INJECTOR TRIMS, NOX LEVELS ARE ALL NORMAL. NO DTCS, NO BULLETINS FOR THIS CONCERN. EXCESSIVE FUEL OR OIL IN EXHAUST SYSTEM WOULD SKEW NOX LEVELS, RESULTING IN EMISSION MESSAGE AT MINIMUM.

The technician said he believes me because the service writer witnessed it himself and said it was an excessive amount of exhaust that was not normal moisture. His best guess is when the car was trying to go through a regen cycle in the cold weather, the excess fuel was condensing inside some of the exhaust system and that aggressive acceleration was then blowing that fuel into smoke that would stream out the exhaust. He said that would contribute to the regen cycle attempts that were lasting about 5 days of intermittent driving, because every time the excess fuel was smoking it would possibly load up the DPF some more and that would keep it trying to regen due to backpressure never decreasing.


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## Barry Allen (Apr 18, 2018)

After a discussion with the dealership service writer yesterday, they're going to write me a check to refund my $100. The writer looked into it and basically said GM was never going to accept it as a warranty thing because they would never be convinced the two things were related (the clouds of blue smoke, horrible fuel economy, then the CEL coming on a week later for a failed temperature sensor). He said the service manager at the dealership is a really decent person and they agreed to refund the $100 diagnostic fee for the smoke problem that they couldn't diagnose.


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## Barry Allen (Apr 18, 2018)

The dealership finally delivered a $100 check this week.


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