My wife’s car had been acting up, running rough , heistation but it normalized out. I replaced the battery, it had a bad cell. That helped , But, the rough idling came back. No “check engine “ light. Popped open the hood and found a vacuum hose, tucked away out of sight. Repaired that. It helped , but the systoms.
My wife drove it to work, barely idling, Check engine on !
Took it in because they have a done work on it last year, and great job. They found the problem, cleared the codes. I dropped it off at my wife’s work and drove it home . It’s running great again. That again .