Hard to start in the mornings

1997 Jimmy 4.3 auto.171,000 Kms. and it is difficult to start in the AM, tune key 5 / 7 seconds, stop, tap gas peddel, turn key 5/7 sec. stop, turn key again, it may start or not. When it starts, it will be ok for the whole day.
Have replaced the fuel filter, air filter, PCV, oil & filer.
Was thinking about replacing the spark plugs, wires, dis. cap, rotor? Or may be I have dirty injectors??
I have no engine warning light, have not changed any O2 sensors.
What do you think?

Had a similar problem with mine.
I'd recommend checking the fuel pressure (should be 60psi or greater for a good start). Pressure gauges are ~$30-50.00.

I provided a link to a thread I started to narrow down finding the leak in the fuel system.

http://www.automotiveforums.com/vbulletin/showthread.php?t=925619&highlight=hard+starting

I also would look into low fuel pressure problems. You need to buy that fuel pressure gauge. I got a neat one off eBay for about $25 plus shipping. The part# is ATD-5567 and it's called "Fuel Injection Tester". I had a 1999 Jimmy that would not run while hot. It turned out to be a bad contact in the fuse block terminals. The pump measured 0 psi while the terminals had insufficient contact. These Jimmys also have poor grounding wires (presumably affecting the fuel pump) that can make the vehicle hard to start. There are two to three grounding rings so don't stop when you find just one. I hope this helps. John