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Air filter fire

I have a 2014 Toyota Sienna that I bought new last year that currently has 10,000 miles on it. I was driving home today when the car stalled, and smoke started coming out of the front. Firefighters came and took out the air filter, which burst into flames. They said they had never seen anything like it before. They looked over the air filter box thoroughly, said there was no more threat of fire damage but that it smelled like an electrical issue, and I had the car towed to the dealership. The dealer called me and said they “found” a cigarette butt and theorized that a lit cigarette was sucked into the air intake, which caused the fire, and furthermore, I would be responsible for paying for the damages, because it was an “outside event” that wasn’t covered under warranty. I do not believe it was a cigarette, because the firemen found no evidence of one, and neither did I when I took pictures of the air filter box. So my question is, is this possible? If so, doesn’t this seem like a pretty big design flaw? I’m concerned that the dealer is just making this up, so they don’t have to pay for anything. If that’s the case, how can I ever feel safe driving this car again?

I’ve never heard of that happening. I mean from the cold air intake system inhaling a cigarette butt and it lodging in the air filter. I suppose it could, but you’d have to be pretty unlucky. If they say they found a cig butt in there, maybe that indeed is what happened though.

Air filters can catch fire sometimes, but it is usually caused by the engine backfiring through the intake manifold. This is caused by a mixture problem, and can happen if there is an ignition or fuel system component out of whack, or even if you are about to run out of gas.

As far as who pays, is there more damage than simply installing a new engine air filter? If it is just the air filter needing replacement, that shouldn’t be overly expensive. Plus you’ll have a new air filter, so that’s one less maintenance item to do on the next tune-up.

I’m skeptical of the cigarette butt claim. Your car insurance will pay for much of the damage, depending on how you have it insured, but I would still press for more information. Make them show you the cigarette butt. If it started the fire, it should be almost completely consumed by the fire. If it looks like a normal butt (burned on one end), contact you insurer and maybe an attorney. Don’t let on you know their ruse is a fake if after inspecting the cigarette butt you believe that it is. Anyway, why wasn’t the butt completely burned, and how did it remain in the air box when the filter was removed?

For the filter to burst into flames, it would have to be saturated with something volatile, like gasoline. Those fumes would have to have come from the positive crankcase ventilation system, and I believe that feeds in well downstream of the filter box.

Unless… there exists a relatively unknown mandate to prevent unburned hydrocarbons from escaping when you shut the engine down. The engine will always shut down with one cylinder on the intake stroke, the injector spraying and the intake valve open. Toyota hides in its air filter housings (you will not find it in the parts list) a carbon filter designed to capture hydrocarbon molecules drifting out of the shut-down engine and hold them until they can be drawn in after restarting the engine. If this were to somehow become saturated by fuel fumes, and somehow was exposed to an ignition source, you’d basically have something analogous to charcoal briquettes saturated with starter fluid. IMHO the probability of this sequence of events happening is about equal to me winning the lottery… three times in the same month… after only having bought four tickets… but I present it as a possibility anyway.

Naw, nevermind. I’m really reaching to the stars with that theory. I’m not buying their story. Problem is, I know not how to prove it wrong short of hiring a forensic analyst.

I can almost hear Tom and Ray say “Bogus” though I can’t possibly type it like they would say it about the cigarette theory. I don’t think you could light an air filter with a cigarette butt if you tried- without an adding gasoline…

Let your comprehensive insurance fight it out with Toyota. You might send a letter reporting this to the National Highway Traffic and Safety Administration with a copy to Toyota because it is a safety issue. As an experiment, you might purchase an air filter and see if you can set it on fire with a cigarette.
I don’t see how the fire would start with the engine running. I would think the engine would suck the fire out. My dad and brother once ran out of gas. My brother primed the carbiretor and the carburetor caught fire. My dad gunned the engine and it sucked the fire out. I’ve been driving for 58 years and have never heard of a cigarette butt being sucked into the air filter and starting a fire.

A glowing cigarette? No.

A glowing cigar? Yes.


While this is very unusual I would never dismiss anything as being too odd. While it was not stated, I tend to read this as:
The firefighters did not disassemble the air cleaner housing.
You took pics of the outside of the air cleaner housing.
Neither one of those says anything about what was going on inside of the housing.

If a butt was the cause then I would assume the dealer has evidence in hand and they should show it to you.
The dealer would also be correct in that this would not be a warrantable repair.

The “cigarette butt” story is bogus. Avoid this dealership in the future because they obviously are a corrupt place of business. Dealerships get a bad rap and this is one of the many reasons why.

I am a volunteer fire fighter, unless there is an injury/fatality or suspected arson, we will get the fire out and make sure it will not re start. We will not do a major cause/origin investigation. Sounds like that is what the fire fighters did here. If a fire was big enough to generate enough smoke to get the fire dept invloved, I would be surpised that the air filter was still intact. A cigratte butt would have been long gone at that point. Get your insurance company involved, let them work it out with the car company.

Thanks for all the input. The dealer is supposed to call me today with an estimate for what it’s going to cost to fix it. I called my insurance company, and they said they will pay for any damages beyond my deductible ($500), which is fine, but I still want to make sure the car will be safe to drive. How do I know it’s not an electrical problem or something else going on that could cause another fire later on? Are there any other tests they could run to make sure no other components were damaged? Or that the origin of the problem wasn’t something else? I’m attaching pictures of the air filter box and the filter after the firemen took it out.

I’m still trying to wrap my head around how the car died in the first place – could the cigarette have caused that to happen so quickly? I had been driving for maybe 10 minutes, and the car just died. I managed to coast into a parking lot, then it shut down completely. After a few minutes, I could restart the car, but then it died again. Only when the hood was opened did we notice smoke trickling out – it wasn’t pouring out or anything. Seems like everything happened far too quickly and almost under laboratory conditions for this to have occurred.

There’s nothing downstream of the air filter that could cause it to burn. So one has to think something was pulled into the intake before the filter to cause it to catch fire.

The reason the engine probably died is, when the filter caught fire it starved air to the mass air flow sensor and the smoke contaminated sensor wire.

So you might have to clean the mass air flow sensor with mass air flow sensor cleaner.


Very interesting pictures. I can’t buy the cigarette butt story. Ask them to demonstrate on a similar car. Rev the motor to 2500 rpm and drop a cold cigarette butt near the intake. See if it gets sucked in. Then ask them how a cigarette butt could even get close to the air intake on a car with the hood closed.

I recently had a fuel injected motor backfire a few times due to a bad distributor cap. A significant backfire sends a strong flame into the airbox which can set the paper in the filter element on fire. If you noticed any hesitation, jerking, or “popping” noises when accelerating - those are backfires.

Both of these explanations are rare, but the cigarette butt just seems unbelievable to me. I think something in the ignition system is out of time, or you may have a valve problem. A burnt exhaust valve for instance. A badly adjusted valve would be ripe to get burned and cause problems at 10,000 miles. A compression test of all cylinders should be done.

There’s no way I can tell what happened from those pics. About the only way the filter could have caught on fire would have been if the intake had inhaled a cigarette or cigar butt, etc. The MAF sensor wire gets very hot but that’s located after the filter; not before and there’s really nothing else in the housing that is electrical.

Just some food for thought. About 15 years ago I was on my way home from Tulsa, OK one night. It was a beautiful night and I had the windows down with the A/C off. About a block in front of me on a winding back highway some guy in a pickup threw a cigarette or cigar butt out the window with sparks flying.
My initial thought was idiot; it’s very dry and the potential for a brush fire exists now.

A few seconds after that the outside edge of my left eye went on fire suddenly and I had to stop instantly. I found a large chunk of ash in the corner of my eye and luckily had a bottle of water in the cup holder to help wash it out.

Point being here that a random chunk of ash from someone’s smoke managed to survive 2-300 feet in the air and into my eye through an open window at highway speed. There’s no reason to think that something similar couldn’t happen with the intake tract which is inhaling a lot of cubic feet of air per minute at speed.

An errant cigarette or ember of some sort is highly unlikely yet it appears to be the most likely scenario here. I don’t see any way the Mass Air Flow sensor could have failed and caused the air filter fire and not be completely melted itself. The sensor is after the airflow from the filter and while the engine was still running any flame or smoke would have been drawn into the engine and not back to the air filter housing.

The MAF needs to be replaced, not cleaned.

Seven years ago a customers car came in with the same condition. The bottom air cleaner box was burned away, filter mostly burned and air box lid melted.A lit cigarette entering the air box seams most likely. The driver would have noticed other sources of fire like fireworks thrown on the road or running over a barbecue grill.

If a lit cigarette lands in the air box it can land on dry leaves and other debris. With the engine running there is a flow of fresh air over the smoldering debris, good for starting a fire.

BTW, your engine stalled because of a lack of oxygen, it was being consumed in the air box fire.

@Nevada_545 may have something there. I had my 2011 Toyota Sienna at the dealer for routine maintenance and they found that squirrels or some such rodents had deposited acorns under the hood. Something like this may account for the OP’s air filter fire.

Check out this recall, Toyota Motor Corp. said Thursday it will recall about 20,000 model year 2014 Avalon, Camry, Highlander and Sienna vehicles and model year 2015 Lexus RX sport-utility vehicles equipped with a certain engine.

EDIT HEADLINE from the link.Fire risk prompts Toyota recall of Camry, Sienna, Highlander, Lexus RX

The automaker said that in cars sold with its 2GR-FE V-6 engine, the end cap on the right-hand fuel delivery pipe in the engine compartment could have been insufficiently welded during manufacturing by the supplier.

I sometimes find cigarette butts in air cleaner boxes and cigarette butts fall onto the floor when removing engine under shields. This week two people thew lit cigarettes at me on the way to work.

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I 'spose anything is possible. I used my gas grill last night for the first time this year. A red squirrel had packed it shredded paper and leaves. I got a whole Walmart bag full out of it. I imagine that would burn pretty good in an air duct.