Do you know any fics handling something like a “happy got us stuck in traffic jam, let’s make the best of it and have sex in the car” – situation?

I think you probably mean like random sex happening, but I’m going to interpret your ask as Car Sex because I don’t really quite know how to find fics like the first and because I want to.  There are also some really different authors on this list, so please check them out and show them some love! (also, if I’ve totally screwed up your ask, please feel free to resend it)

Start your engines! Vrrrroooom! Vrrroooom!

IS THAT A STICK SHIFT OR ARE YOU JUST HAPPY TO LEAVE COMMENTS AND KUDOS?

Revved Up by chibimono:
Tony likes that new car smell and Steve.

Debriefing in Tony’s Car by MakikoIgami:
People are usually surprised how agile Captain America is, despite the bulk of his muscles, his sheer height and weight. Likewise,
people were usually not so surprised that Iron Man wasn’t so agile on
the ground and close combat. He usually excelled at air combat and
elaborate and – admittedly – flashy maneuvers that took him out of the
enemy’s range.
However, the roles were pretty reversed when it came to Steve Rogers and Tony Stark in the confines of a car.

let’s get it on by colourexplosion:
“Let’s Get It On” comes on the radio in the car, so obviously Tony and Steve do. (I think this is actually kind of your ask)

A Different Kind of Hunger by Impala_Chick:
Tony’s fancy car provides Steve the perfect opportunity to execute his
plan: the one that involves taking Tony’s cock down his throat.

It’s a workshop, not a sexshop, Steve by BeamsnBows:
Steve teaches Tony that you CAN play where you work. Tony’s not too happy about it.

I’m Out of Touch, I’m Out of Love by StarSpangledCap:
Steve and Tony fuck each other when they get stressed over Avengers
stuff. This one just happens to be in a car in a remotely empty area.

Cherry Ride by copperbadge:
A SHIELD agent named Roger Stevens told Tony that his nickname was
“Cap”. Tony didn’t connect the dots until it was much, much too late.

Cars and Seat Belts by Notevenwinded:
Steve decides that he needs to put in better use Tony’s huge car collection.

Vintage by jynx:
Steve had always liked vintage cars.

The Highest Form of Friendship by @chibisquirt:
“Imagine if I’d met you back in my hellion days,” Tony says, and Steve groans out loud.

There’s a mental image, here.  Well, Steve’s a visual kind of guy; mental images are how he operates.
The mental image is of a baby Tony – okay, not baby; Heyday
Tony, let’s call him – and Heyday Tony has dark eyes and a wide mouth,
and the little pin-scratch frown that Nowadays Tony wears all the time
these days has been magically retrotransformed into a confident smirk.
Heyday Tony has the same lean strength that Nowadays Tony has, but he looks
taller because he bears himself more aggressively, more
straight-backed.  Heyday Tony has poofy hair and a tendency to look all
the way down, and all the way back up, at a person – regardless of
gender – before meeting their eyes.
Steve knows: he’s seen the videos.
Has maybe studied the videos.  Has maybe spent more time on that activity than strictly appropriate…“Can we not?” he pleads. “It didn’t happen that way, and it did happen this way, and that’s how it is.”

Dominant Steve, Jealous Steve, Possessive Steve are all Tony’s Favorite Steve by yuniesan:
During a Gala Event for the Avengers, Steve makes Tony wear two things, a
butt plug and a cock ring. He’s already slicked up with lube and ready
for Steve at any time, but Steve wants to make him wait until they get
home because he has other plans for their night.

(limo sex)

One Hell of a Wild Ride by @missbeckywrites:
A recon mission turns into something a little more than Steve and Tony bargained for. Good thing Tony’s got a fast car.

(not exactly car sex, but, um…there are cars)

Paint Job by @cptxrogers:
“You want me to what?” Steve looked incredulous.
“I want you to detail my car,” Tony said with a smirk.

Down on the Farm by tellxmebby:
Tony laughs, throwing an old rag at the blond man, who bats it away in the air. “Fuck you.”

“Mm,” Steve rolls back under the car with a newly fitted socket, “maybe later.”
Steve grins up at the chrome above him at the lack of
response. It must take Tony a minute to recover, but when he does Steve
hears him huff. (a car is, well, featured?  idk)

Also, Motorcycles b/c why not?

easy rider by ohmyloki:
Tony likes Steve. He likes having sex with Steve. He loves how Steve
looks on his motorcycle. It just makes sense that he’d want to combine a
few of his favorite things.

Of Motorcycles and Leather by MikaJurgen:
Tony and Steve have a little fun on the back of Steve’s bike.

Riding Dirty by Professor_Fluffy:
Motorcycle Porn.

Sex on the Bike by morphia:
Tony gets an idea. Steve likes the idea. Sex happens.

Strategic Reinforcement by antigrav_vector:
Tony is working late again, and Steve is tired of waiting. Going down to
the workshop reveals something astonishing, and what else is a man to
do when presented with something like that, except reward his boyfriend?

Episode 1: Hot Ride by @queendophne:
Steve just wanted to surprise Tony with a personally made bike. He did
not mean for it to go this far. Will Tony understand? Or will it be over
for Steven G. Rogers?

Burning Rubber by @ashes0909: The two of them, they’re in a new place in their
friendship. Tony had flirted one too many times and Steve had finally
reacted with a flirtation of his own. A tease about Tony’s pretty face
that had shut him up quicker than the Avengers Assemble signal. The Avenger’s call, he expects to happen. Steve Rogers flirting with him? That is something entirely new. And now Steve’s mostly naked in the garage.

Conga Line by Avidreader6:
Tony doesn’t remember the night before until he’s woken up by a phone call from a policeman.

(not sex, but a good Steve’s bike fic)

Yet Grows All the Richer by Dormammu:
It’s the New Year’s Eve party at the Avengers Tower, all the Avengers
who could attend are there. Steve is in his own corner, drinking Coke
and thinking about his teammates. Then about other things, shiny things
being touched by rough, clever hands…

The Bike the Dad Built by @theactualcluegirl:
Tony’s dad never built HIM a motorcycle…

(not porn, but an interesting look at Steve and his bike part of series, but can be read alone)