Intermittent hard starting (firing) and rough idle

I have a '97 Blazer 4.3L "W" engine with hard starting (firing) and rough idle.
Use to be able to just hit the key and it would start. Intermittent Service engine light, seems to go away after some highway driving. Long idle seems to activate the Service engine light..
It has descent fuel mileage (19 city/22highway) and great acceleration.
It’s just the starting and idle that’s an annoyance and worrying about if this is a start to a bigger problem.
Check battery voltage 12.4 v. I’ll check the fuel pressure next and was going to check the plugs again, and see if I can get service codes when the Service engine light is on. Also I was going to check the ERG continuity.
Did the following tune up: plugs at 100K, wires, cap, rotor, fuel filter at 109K.
I visually checked hoses, for vacuum and fluid leaks, none I could see or hear.
Any ideas/methods for analysis would be appreciated.

go get your codes scanned at autozone for free.

Your code will be stored a short time after the light goes out. Even though they tell you otherwise, the light doesn't have to be on to pull the codes.


How long ago was the tune up? What kind of plugs and wires did you use?

Finally had some time to find out the problem.
Toooo much work.
I took it to three different Auto Zones over several weeks, and they all said "multi-miss fire",they said they couldn't get the numerical code that their hand unit converted the code no. to text.
I bought a book and did every voltage/ohms check I could do, pulled three of the four O2 sensors, etc., all no joy. The engine service light began to stay on longer, even continuous for a month. I started to notice a significant fuel smell out the exhaust. Also the gas mileage was beginning to drop. Note: the only symptom was hard starting and rough idle. Also if I did not drive for a few a days the plenum would evidently dry out and it would start and idle fine for a few minutes. I called a local garage which I had used before and they would do a test for $45, I jumped on that, wouldn't you know the night before the engine service light went out (really didn't matter because the codes are kept). Anyway, within 20 minutes they called and it was the Fuel pressure regulator diaphragm was leaking. I would like to have done the job myself, but just not enough hours in the day. They fixed in 2 1/2 hours, starts and idles great. Other data:113,000 miles on this '97, looks and runs great and really I can't complain. I have owned it for 7 years and it has been a very dependable nice ride. Hope this might help some else.