Jeep Repair: Check engine light on, jeep grand cherokee, altenator

Question
I have a 2003 Jeep Grand Cherokee. It has approx 61,000 miles on it. It's back in the shop for the fourth time in as many weeks. The first time I took it in, it started sputtering and kicking as I was going down the highway. The check enging light was "flashing" I turned around and went directly to my mechanic. He replaced the sparkplugs and it ran terrific for about a day. The light came back on and was flashing intermittently.  When it was scanned, it said there was a problem withe the fifth injector. That was replaced. When we started driving it again, the light immediately came back on solid, not flashing. We took it to the dealer.  They told is the spark plugs that were put in were the wrong ones.  They put in the "correct" plugs and also told us that the altenator was screaming. That was replaced. We brought the jeep home. It ran ok. After a couple of days the check engine light came on then went off.  It was off for about almost a week then when I was driving it started sputtering and kicking, the check engine light started flashing. I got it home, called the dealer.  He couldn't take it for almost a week. In the meantime when it was driven, the check engine light was on solid.  Other than some slight sputtering, it ran fine. We took it to the dealer and when we called to see what the problem was, he said he didn't know yet but it may be a craked head or a valve. Based I what I've written, is it possible that could be the problem?  I feel I'm getting the run around from the dealer.

Answer
U know what u can do for me to help u out with this is get the dealer to give u the Code numbers  Tell them U want them all of them. I am not going to go by what some one says untill i get as much info as I can get    ooo BTW  do u have a 4.7L engine V8?? And if u can remember  what was the first check engine light codes that u had when u first took it in for  or all of them if u can recall.