This phase I trial is studying the side effects and best dose of flavopiridol when given together with gemcitabine and irinotecan in treating patients with unresectable or metastatic solid tumors. Drugs used in chemotherapy, such as flavopiridol, gemcitabine, and irinotecan, work in different ways to stop tumor cells from dividing so they stop growing or die. Combining more than one drug may kill more tumor cells