Ok, I have done TONS of searching online and here as well. I have yet to find someone with a problem similar to mine that has guided me. So, in February I had a new catalytic converter put on, changed spark plugs, wires, cap and rotor. I did all this because a)it was time and b) in march I was moving from Nebraska to California.

Car was running fine after all this. When we were passing through Nevada my car through up a P0300 code. It was very close to our over night stop so we got there and the next morning the code was gone.

Around mid march I got the code again. So I knew my fuel filter needed to be replaced so I had my car in the shop for that and a fuel system cleaning. Two weeks after I got my car back my fuel pump died. That was when problems started. A few days leading up to my fuel pump dieing I was getting a rough idle and shuddering at low speeds. Once I would get over 25 mph my car would run great. So after my fuel pump was replaced in early to mid april everything ran fine for a couple of weeks.

Then in may my problem with rough idle and shuddering at low speeds is back. But this time its not consistent, at all. Sometimes my car will run fine, other times not. It has been a huge PIA to get this figured out. Yesterday I was finally able to get my car to idle rough while I was actually able to pop the hood. I noticed a spark sound, like when you turn on a gas stove. Which leads me to believe a cyclinder is sparking but not firing.

So, I dont know where to turn right now. Should I get in and test/clean my fuel injectors? Even though that was(supposedly) done in march. 1999 Blazer 4.3L 4x4, 115k miles. I do not have a check engine light.

OH, I have not had any temp problems.

EDIT: When my air is turned on, the rough idle is more persistant.

 

Try starting it in the dark and watch for sparks at the cap and wires. Take a spray bottle filled with water and spray the cap and wires and see if it makes a difference while it's running.

 

So, my car has pretty much sat since I started this thread. Today I was able to finally get to start trouble shooting. I pulled off my cap and rotor and they both look fine. I need to get and ohm meter to actually test my wires but the boots all looked well. I only had time to pull plugs 1, 3 and 5 and all three were miss gapped. They were all too big. After putting them back in I took it for a short drive to the store and it drove fine. Accelerated well from every stop. I had no stuttering when idling in drive. Tonight I am having a friend over so I am going to go out and turn it over in the dark to check for sparks. Tomorrow I will be pulling the other three plugs to see if they are gapped correctly. Fingers crossed that this was the problem. One thing I am wondering, and why I am posting an update. Could plugs that are gapped to big cause a come and go problem? Also would it explain why at low speeds it would be sluggish on acceleration?

 

i am having a similar problem lately...rough going up till 30mph then all is good.
idles great...its just that initial getting going that does it. i will look at my gap when i get a day off, later in the week.

good luck, keep us posted.

 

The idling problem is what really throws me off because it only happens when I am in drive or reverse. When I put my car in neutral or park it doesnt do it. But it didnt do it at all tonight so, maybe since(so far) three plugs were miss gapped that it was causing the the idle issue.