Lindsay Lohan -- Mad Race to Complete Community Service

Lindsay Lohan is scrambling to finish her community service by Wednesday ... because jail is on the line.

We're told Lindsay went to the Community Service Volunteers in London Friday and Saturday, and her plan was to go Sunday ... and Monday and Tuesday. She's been delinquent 15 days and MUST finish them by court Wednesday morning. She says she'll get it done.

As TMZ reported ... Lindsay was supposed to do 30 days community service by November 6 but only finished half. The judge cut her a break and ordered her to finish by Wednesday. Lindsay has lots of excuses for not finishing up to now. CSV was closed for 2 weeks, she was in Bora Bora, and on and on.

And we reported she was in the hospital last week ... she told her people she contracted Chikungunya in Bora Bora, but even some of them think she checked herself in just to create an excuse.

She's now acting like she'll log in the necessary hours, but stay tuned. She has a rich history of violating probation. And she'll face a new judge Wednesday and it's likely if she's delinquent the prosecutor will recommend jail.

Lindsay is on probation for her 2012 reckless driving case when she slammed into an 18-wheeler.

Give her this ... she's reliable.