I'm a mechanic, so by my nature I like to know how things work. I get a feeling of joy when I see how the magic happens. When you first get the itch to try repairs yourself there are many magical obstacles before you. For example, look at changing gears on a bike. You are pedaling a bike, you move the lever on the bar *POOF* magic happens! and now the bike is pedaling easier up the hill.
But then you spend a few minutes with your bike up on a stand. You spin the crank and it's hard to turn, so you you click the lever. Then the funky arm moves, the chain jumps to a bigger gear in back and it becomes easier to pedal. Your brain absorbs the idea of what is happening and suddenly the magic is gone. You see the little wire that pulled the funky arm and there's really no magic at all.
Most people are happy as long as the magic happens when they want it. Everyone faces their own challenges everyday and everyone is a magician for their own specific magic. I send my kids to school, *magic happens* they come back smarter. I send money to the City of Longmont *magic happens* my lights stay on and I have running water. I get a shot in my arm *magic happens* I don't get sick.
All of us like to sit in a car turn the key, and *poof* the car turns on. This post is about one car in particular, it's also about a magical light.
This is a magical light because it helps me make the money I send to City of Longmont. Most of my career has been about keeping Check Engine Lights (CEL) off, usually it's in big trucks and heavy equipment. But the light comes on in my 2000 Audi A4 so I wanted to learn more about it.
I've owned my Audi since '17 so I've had some time to get into it. I had to put an engine in it, I've replaced brakes and wheel bearings. Plus I've chased some electrical issues. I've got most everything under control, everything except the CEL and the singular code that it throws # 0441.
The CEL was introduced when computers were added to engines. The computers were added to help control the emissions components. Basically cars and trucks and bulldozers all have emissions devices to help them run cleaner. It's one step in lowering greenhouse gasses and it's been extremely successful. The only issue is that things wear out. Screws come loose, shoelaces snap, eventually everything breaks down it's called entropy. So back to my 22 year old car and code # 0441. This is a generic code that means the same thing to every manufacturer. Audi defines it as "EVAP System Incorrect Purge Flow."
Until the 1970's gas tanks just had a hole at the top to act as a vent. This worked to let air in and out of the tank but it also bled fuel vapors into the air. To clean things up a system was added to catch those vapors and then add them back to the engine when the car was driving along. This is the EVAP system, it's the one mentioned in the code description.
The basic idea of the system is that fuel vapors vent off the fuel tank and get trapped in a canister filled with charcoal. This EVAP canister is in the rear of the car in a little compartment under the spare tire.
When the pump kicks on it pulls air through this paper filter and pressurizes the EVAP system to a specific amount. If the correct pressure is reached a small switch in the pump triggers and the ECM begins counting how long the system can hold the pressure. This is the crux moment. This is the point where my car passes the test in the summer, and fails in the winter. I have the dreaded 'intermittent' failure. The pump kicks on, ECM runs the test and the pressure bleeds off too fast. Then the CEL comes on and a #0441 code is logged.
I could do better diagnostics. I could jump power to the LDP and try to pressurize the system myself. Then I could check for leaks with soapy water or I could use a fancy smoke leak detector. But the thing is...I still don't care. My car passes emissions because this fault doesn't happen when they run it on the dyno.