How many miles on the engine? I had to replace the timing chain on my engine at 70,000 miles. If, when they did the tune up, they didn't check for a jumped tooth on the timing gear, then the timing would be too far advanced, and cause the hard starting problems. One way to check this, is to turn the harmonic balancer in one direction, with the distributor cap removed,, and keep turning until the timing mark is located at the 0 degree mark on the timing tab. Then, turn the harmonic balancer in the opposite direction slowly, watching the distributor rotor pointer, until it moves, and then stop. Compare where the timing mark is in relationship to the timing tab. If you find that it has moved more than 1/8" to 1/4", the timing chain has stretched, and most likely has jumped a tooth.