An auction listing that says “mechanical damage” can mean almost anything, even on an Audi S4. It might be a dead battery, or it might be a ruined engine. Buyers who bid anyway are betting on the cheap fix.
The self-described body guy behind @BackYardBoyz, who goes by Tim, made that bet on a heavily modified 2021 Audi S4. “I just risked $13,000 on this 2021 Audi S4 from Copart with mechanical damage,” he says. The winning bid was $11,700, and fees brought it to about $13,000.
He admits he bought it partly on impulse. It had a gray body, a red interior and 76,000 miles. Also, it wore a sticker from a local tuning shop.
It Runs, But It Misfires
When the tow driver put a jump pack on it, the S4 started right up and idled well. It even went into reverse. So where was the mechanical damage? Once he put it in its sportiest drive mode and revved it, the misfire was obvious.
Next, his first scan showed 46 trouble codes. After he cleared them, six remained, including an oxygen sensor code. He thinks many of the others came from a dead battery.
The Shop That Built It
So Tim called the shop on the sticker. The owner, David, recognized the car right away. “I built that car. It did leave in perfect running order,” he wrote, Tim says, and he invited him to bring it in.
At the shop, David filled in the history. In his account, a dealer had quoted the earlier owner $33,000 for a new engine. David says the real problem was a failed rocker arm. So the shop replaced all 24 rocker arms and a damaged camshaft, then added a long list of bolt-on upgrades.
Initially, they fitted a missing oxygen sensor. The car still misfired. Next, they ran a borescope down each cylinder and did a compression test. The cylinders looked good, and compression was healthy across all six, in the range of about 150 to 170 psi on their gauge.
New Plugs, Then A Gritty Surprise
Then David fitted new spark plugs, gapped to spec, and updated the engine and transmission software. After that, the misfire was gone. On the test drive, both men said it ran perfectly.
However, there was a catch. While they had the oil filter off, they spotted small bits of debris in it, even though the oil looked brand new. After the drive, they drained the oil and found fine, gritty material in it. They also found the same kind of grit in the intake charge pipe.
Tim is calling it sand. David, however, is less sure. “It’s not sand. Look,” one of them says while rubbing it between his fingers. It smears out under a fingertip, and neither man could say for sure what it is.
Meanwhile, they could not explain how the same material ended up in two separate systems. “I have no idea where that sand came from,” Tim says.
What To Check On An Auction Car Sold With Mechanical Damage
- Try to start it before you sink money into it. A jump pack can tell you a lot.
- Clear old codes and scan again. A dead battery can set off a long list of false alarms.
- Ask whoever worked on the car before. A shop’s records can explain what changed.
- Do the basic tests. A borescope look and a compression test can rule out major engine damage.
- Cut open the oil filter and check the oil, even if the car runs well. Debris can tell a different story.
Where Things Stand With The Audi S4
For now, the S4 runs and drives well, with new plugs and updated software. The source of the gritty material is still unknown. Tim says he wants to know whether the engine could fail in 100 miles, and he is asking for advice before he decides what to do with the car.
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