Reddit mentions of Royal Purple 18000 Max Atomizer Fuel Injector Cleaner - 6 oz.

Thing 2: Your combustion system sounds like it could probably be cleaned.

To grossly oversimplify internal combustion engines, here’s a quick rundown of how they work: Gas gets spritzed into the combustion chamber (this is the part with cylinders and pistons) while fresh, outside air gets sucked in and filtered (this is the part they mean when they say intake manifold). The fuel spritz is controlled by the aptly-named fuel injection and increases when you put your foot down on the pedal. At the same time, the amount of air that comes in is controlled by the throttle body assembly, which opens and closes based on your acceleration. More pedal = more gas and more air. The air and the gas combine and the spark plug fires, igniting the mixture. Tiny explosion forces the piston upward in the cylinder with force, which moves crankshaft, which in turn moves all the other things and ta-daaa! You can go places in your car! More pedal, more gas, more air, more tiny booms, you go zoom! Very fun.

The problem is that modern gas isn’t 100% pure, and it leaves a residue when it ignites. It’s a black carbon deposit that’s almost identical to the soot that collects on the side of a glass candle except there’s way more of it, it’s way stickier and it’s made from the restless ghosts of all those dead dinosaurs you burn up every day to get to work. This residue probably has a real name but I’ve only ever heard it called carb, as in, “the engine is all carbed up so run a bottle of gum-out through it.”

What happens when this shit gets left behind is that it collects on your throttle body plate, which then can get stuck and not open and close appropriately. It can also collect on the little zappy ends of your spark plugs, which means they don’t fire as efficiently. Now without the right air/gas mix, and without the right booms, you no go zoom. And then, your engine is less efficient at burning the fuel in the first place, which means more uncombusted sediment and shit gets left behind and the whole thing becomes exponentially worse. The main sign of all of this is starting your car cold and, while still in park, seeing if your RPM needle bounces as the engine lopes, like Womp...Womp...Womp. If you feel like you need to punch the gas a little to keep it from stalling, that’s a sure sign.

But it doesn’t have to be that bad to need cleaning, and I generally believe that every car that’s not new could use it. Your fuel efficiency will improve and the smell your boyfriend smelled should go away. Shops call this service a fuel system clean, pre-combustion service or an ignition clean, but basically it’s any service that cleans your throttle body, combustion chamber, mass air flow and O2 sensors. You can have it done, or you can run several treatments through your gas tank to approximate this. I like this one but you can get Seafoam or Marvel Mystery Oil at any auto parts store, too. Cleaningvthe fuel injectors and valves that way and changing out your spark plugs should improve things a bit.

Pro tip: if you have any parts replaced, always have them show you the old part and the new one after it’s installed, if it’s visible. This is an easy way to discourage the most blatant fraudulent deception (charging for new parts not installed), though some shops will find other ways. If they tell you something else is wrong, make them show you. Ask to see the OBD codes. In my experience (being a woman) this causes no problems when you feign curiosity, like “ooh, can I see what that looks like?”

Oh, and, one more thing. If you have the belt/tensioner done and your AC doesn’t immediately blow cold again, have them check the relay/fuse. There’s a fuse box under the hood (in addition to the one by your steering wheel) with a fuse that controls the compressor; if it tried to kick in but your belt wasn’t running it, it could have blown that fuse. It’s a bit frustrating at first when you think you did all you could to fix it but it still doesn’t work and then you remember the fuse. Went through that on my husband’s car.

I know it’s a lot of information but I hope you feel better prepared. The not knowing what’s wrong or what could go wrong with my car is really anxiety-inducing for me, so I hope I’ve helped clear some of that for you.

Let me know how it goes, please!