Check the spark plug gap.

 

Yeah. Tune up and a fuel pressure check wouldn't be a bad idea either. I think you need about 13 -20 PSI on the tTBI units but cinsult your repair manual for that spec (please don't tell us you don't have one) to be sure.

 

I agree, check the CEL. It's easy with a paperclip as a jumper.

My blazer recently had this problem. It would not start unless I kept the pedal to the floor and cranked it for a good 30 seconds. The idle would stay low for around 5 minutes so I had to give it gas to keep it going until it got warm.

The CEL said the coolant temperature sensor was bad. I checked it with a multimeter and sure enough it was bad. You can check it really easily with a basic multimeter, just read the resistance across the pins. It should read close to 2800ohms at room temperature. A higher temperature reads less resistance and colder reads higher.

The code for a bad ECS is either 14 or 15.

Edit: Why have you not read the code. It will likely tell you what the problem is. Why randomly replace things when the engine is trying to tell you what is wrong?