OBJECTIVES: I. Determine the maximum tolerated dose of irinotecan, fluorouracil, and leucovorin calcium (Saltz regimen vs Mayo regimen) plus oxaliplatin (arm I vs arm II) in patients with metastatic or unresectable solid tumors. II. Determine the effect of irinotecan on the disposition of oxaliplatin in these patients. III. Assess the development of peripheral neuropathy in these patients on the Mayo regimen. IV. Determine the activity of these regimens in patients with metastatic solid tumors.