I recently bought a 96' Blazer thats in great condition. The only problem is a rough idle and it sputters and misses when Im accelerating.
It seems to get worse as it warms up. When I start it in the morning the hesitation off idle seems minimal and it accelerates strongly. But after driving for about 5 minutes or so and the engine is warmed up the rough idle seems worse and the smooth acceleration is gone, replaced by missing and skipping while I'm leaving a stop sign.
I've replaced the plugs and wires, pcv valve, Mass Airflow Sensor, air filter, and cleaned the EGR valve.
The MAF seemed to help some but the problem is still there.
Anyone out there had the same problem and found a solution?
Any suggestions would be appreciated... i'm pulling my hair out trying to figure this out!

 

How does the cap & rotor look?

 

Visually the cap looks fine but that doesnt mean it couldnt be cracked. I did go out one night and watch it while it was running in the dark to see if I could see any arcing but I saw nothing.
Could the rotor cause the problem? I suppose if it's bad it might when the timing changes during warm-up.

 

You probably won't see any arcing if there is a problem inside the cap. The cap & rotor are just as important to replace as the wires when doing a tune up. I would start there with quality parts.

For some reason, these trucks only like AC Delco ignition components. Many members have chased misfire/hesitation problems round and round only to find out that the brand new "insert aftermarket brand name here" cap & rotor exhibited the same problem as the old cap & rotor they removed.

 

Thanks... I'll give that a shot and see what happens.

 

Put the new cap and rotor on today and so far no difference that I can see.
This could also be a vacuum hose problem right? I know that can throw everything out of wack.

Another thought.... the coil?

 

could also be a fuel filter problem. try changing the filter and see if that solves your problem.

 

I went to Autozone today to buy a fuel filter, but before I did I asked the guy at the counter to check for codes. the first time I had them do this a couple weeks ago I got the p0300, p1153, and p0102. Now since putting the parts on I posted earlier I'm only getting the no. 3 cylinder misfire code.
Now I failed to mention earlier that when changing the plugs and wires before I gave up on plug 3 and left the old one in because it was a nightmare and I just couldnt get it out due to the steering shaft being in the way.
I guess I'm being optomistic but since I'm getting the no.3 code I'm going to give it another whirl tonight and see if I can get it out.
I'll let you know how it goes.

Well... I got it out. destroyed it in the process. I ended up having to disconnect the steering shaft to finally get at the plug. What a pain.
In any case, it seems to be idling fine now and when I give it some gas there isnt any more hiccuping or hesitation. Now I'll need to take it out for a drive to be sure, but I think I got this problem licked.

 

To get that plug out I took a long extenion and ground the corners so it became a wobble end then I ground the shaft where it hits the steering column. I put it in my special tool drawer and have used it twice. Works just fine.

 

Long wobble extension, rotating adapter and an medium extension. jack the front end up, remove the driver wheel and the rest is a puzzle of how you prefer. I went socket-adapter-long extension-medium extension over the steering shaft. Made it quick and easy afyer I figured the combo out.