2004 Jeep Cherokee

Engine Performance problem
2004 Jeep Cherokee Four Wheel Drive Automatic 54,000 miles

In January, the check engine light came on so I had to have a sensor replaced-costs over $300.
Then about 5 months ago the check engine light
started coming on then would go off. Then about
a month ago, I would start driving and it would jerk and the speedometer and rpm gauge would fall and it would do this several times and quit. I took it to a mechanic and they hooked it up to a machine and drove it and said it would register the problem and didn't do it when they drove it. I had to take it back again-same problem-they didn't the same thing. Couldn't find the problem and said maybe was the fuel filter and changed the fuel filter-cost around $95.00. Took home and the next week on Wednesday and then again on Sunday, when I started driving it did it several times. This time worse than ever! It would Jerk and the speedometer, rpm, and once the gas gauge would fall, and sometimes it would die. I took it back and they said it was due for a complete tune up. They said the battery cables were loose, and two of the sparks plugs were set too wide. They changed all the transmission fluid, filter, spark plugs, oil, filter, axle pinion seal, pinion shaft seal, rear end gear oil, rear differential housing cover and charged me $458. Tehy said it was done Thursday at 5 pm. I went to pick it up and he took it for a test drive and when it brought it back and he tried 3 times to start it before it started and then it would die when he put it in reverse. They kept again last night and said they would work on it again this morning. Help!