It seems like that still turns up in contemporary crime shows. “Oh, was that the shot that killed Uncle Jehoshaphat? I thought it was a car backfiring.” I can’t remember the last time I heard a car backfire. Do modern cars even do it?
I doubt the modern computer chip ignition would allow a backfire.
I haven’t heard a car backfire in over twenty years.
Can fuel injection cause a backfire? That may have only been a thing with carburetors.
They can, but it doesn’t happen often. Last time I had one was when I was going up a really steep hill slow but under a lot of RPM when an ignition coil pack failed and caused a huge misfire in cylinder #1. Just the one bang, but then it ran like crap after until I got the pack replaced. Immediate check engine light, of course.
Yes, cars can still backfire.
But, it’s rare, and means that something is seriously wrong with the engine, like a bad crank position sensor or burned intake value. And, a backfire is likely to kill the MAF sensor, so it’s not something you can to have happen to your car.
ETA: note that a true backfire is NOT an explosion out of the exhaust, but rather, back through the intake.
Hmmm… sounds like there are more random gunshots in today’s world than car backfires.
WAY more. 
A couple of lives ago my older cousin had a “jalopy.” My uncle had a dairy farm on a dirt road; nothing around but other farms, pastures, and woods so the unlicensed jalopy got driven all over the pastures, roads, whatever. It was a mid- late-'40s Chevy.
Sometimes when we were going down a long hill he would shut the key off, pump the gas pedal, turn the key back on and it would backfire through the exhaust. We all got a big laugh out of it. He couldn’t blow the muffler off because it didn’t have one.
As others already noted, I don’t think a modern car would do it unless there was something wrong with the computer-controlled fuel or ignition systems.
Not a backfire (which I haven’t heard in years, and even then not from a normal modern car), but what is the popping noise some cars make, apparently from the exhaust, when accelerating hard from low speed?
During deceleration, performance cars may have lean misfire, which results in some unburned gas entering the exhaust. When the car accelerates (or even during decel), that gas can ignite, resulting in the pops.
Most common on motorcycles but some drift-like cars seem to tune for that effect.
And in case you ever wondered about the flames ----- igniters in the pipes and hidden tanks of propane. Its one of the reasons I have two sets of saddlebags to fit my one bike.
My bike does that quite a bit on closed throttle. My Elise would crackle a lot as well, partly because of the performance tune, and partly because of the very short, minimally muffled exhaust.
For my current car, BMW sells a performance tune that among other things, adds burbling and popping on lift throttle.
Do they also sell “burns lots of oil and needs a new clutch”? I had a car with those features. 
“Was that a car backfiring?”
“Nah, probably just some gunshot.”
mmm
Ba-da-bing!
(That was a ricochet.)
I had a 1961 Falcon back in the 1990s. It was backfiring when I pulled it into a stop. I decided to figure out why, and started by pulling out the sparkplugs. One of them for some reason was gapped way too wide. I don’t know how that happened. I don’t know if a misfire from the distributor could do that-- it wasn’t pitted, just gapped wide. I regapped it to spec, and the backfire went away.
It used to be, and was with the plugs for this car, that you bought sparkplugs that might fit a number of models of cars, and gapped them yourself to whatever your particular car needed. If you made a mistake, or whatever had happened to my plug happened, you got a backfire.
Now, plugs come gapped already, for your model. You tell the auto parts store your model and type of engine, and they give you plugs that are already gapped. So there is no chance of you making a mistake, and over-gapping a plug. Also, assuming that some hiccup with the distributor had caused the gap problem in my plug (it wasn’t me, because it had run fine for months since I had installed the plugs, then suddenly started to backfire), it can’t happen now, because cars don’t have distributors anymore. The timing is controlled by the CPU, and if it’s off, instead of engine performance problems, you may get a failsafe shutdown instead.
I’m assuming that other timing problems could probably cause backfires, and you would have to correct them yourself, after hearing the backfire. Now, mostly cars self-correct, but like I said, if they can’t, they often go into a failsafe shutdown.
FWIW, though, a backfire really does sound like a gunshot. I’ve had other things, like a tire blow-out when I hit a piece of plastic, I assume from an accident, and it was a loud noise, but it didn’t sound like a gunshot. I also had a muffler blow once, and it was a really loud noise, but it didn’t sound like a gunshot either. So changing the script to say that someone blew a tire doesn’t really work.
I guess you can include some kind of information in the script like, “The neighbor has a '56 Packard,” when you say a car has backfired. It’s a little specious, but it’s better than suggesting that the neighbor’s 2015 Toyota has backfired.
On more than one occasion when we were watching a ‘true crime show’ (e.g., Homicide Hunter) and a detective asks a (usually female) witness whether she’d heard a car backfiring instead of a gunshot, I’ve said to Mrs. L.A. 'When was the last time you heard a car backfire? :dubious: ’
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Well, if the witness is older than 50, and is from a mid-sized town, which is to say, one where there’s not a lot of handgun fire from drug gangs, but it’s not such a rural area, that you’re likely to hear people shooting at coyotes near the chickens, she might not know what gunfire sounds like. And she might be a little scandalized by the suggestion that she did; but a car back-firing, that she knows. Stories, she could tell you. Maybe old stories, but stories.
Now, if you ask someone under 35 if they’ve heard a car backfire, they’re likely to look at you like you asked them if they heard the “ding” on a manual typewriter, and if they’re under 30, they’re probably not going to know what you are talking about unless they watch a lot of TCM. And they’re less scandalized by the idea that they might have heard a gun fire at some point in their lives. In fact, they’re a little insulted if you suggest they don’t know what a gun sounds like (even if they don’t). Them, you just come out ans ask.
So yeah, I can see a cop being politic in choosing to ask the question that way with some witnesses.
With a child, who might not know from gunfire, you might ask them if they heard a firecracker go off.
It just depends on the witness.
The last time I heard a car backfire was in 1988. I’d never heard one before, and thought it was a gunshot for a moment.
I don’t think that they are so rare that young people will have never heard them.
E.g., 2-3 years ago a friend of the neighbor across the street used her driveway to work on his vehicle. Every time he tried to start it up it backfired it seemed. So quite a few times over about a week. (I think most things he was doing were making things worse, IMHO.)
Yeah, quite rare under “normal” operation but not everything is normal.
It probably depends where you live, too. In Indiana, there are no standards for cars whatsoever. You can drive around with a plastic trash bag where one of your doors, or your rear window should be. You can have a spiderweb crack right over the driver’s side view of the windshield. You can be missing your hood. Your bumper can be a log held on with duct tape and bungee cords. You can spew a black cloud every time you leave an intersection, like a scared octopus. You can be dragging your muffler so it makes sparks. No problem.
Not to mention, there is no city here with anything like reliable public transportation. Even in Indianapolis, the buses run once an hour. Maybe once a half hour downtown during rush hour. The college towns aren’t any better. So it’s not like New York, where if you are poor, you just take the bus. Here, if you are poor, you have some car you paid a few hundred dollars for third or fourth hand, and work on yourself. You get parts, even tires, from a junkyard.
So there are a lot of really old cars on the road here, and a lot of newer cars in really crap shape. If you want to hear a car backfire, come hang out in one of the dicier neighborhoods in Indianapolis for a while, and you have a decent chance of hearing one.
You are not going to hear one in California, though, where the emissions standards are so tight, that manufacturers make one set of cars to sell in California, and one set for the rest of the country. My brother lives in LA, and was worried his four year old Prius wasn’t going to pass (even though he’s totally anal about maintenance), so he paid for a pre-inspection inspection. No car has backfired in California since 1972. When they need a backfire in a movie, the Foley artists create it. Probably by firing a starter’s pistol.
I don’t know where the “Homicide Hunter” or whatever show was, but if it was in Indiana, then it would be reasonable to ask about backfire-- albeit, most people here have heard gunfire too, and don’t mind admitting it.