i have a 1995 chevy s10 blazer with the 4.3 v6. it has 2xx,xxx miles on it. my problem is that it has a rough idle. at first it was a constant almost dieing idle. we checked the sparked plugs and secured some more tightly and now it runs pretty smooth but when u press the throttle at all it goes into rough idle again for a few minutes then back to normal. what i need to know is what else could be causing it to do this?

 

It could be the spider (fuel injector) dumping fuel, also check the EGR. They are known to foul up with carbon.

 

^^This. If it idles smooth but jumps around under load its either fuel or air (most likly fuel). Check the filters in the fuel system too with 200,000 miles they should have been replaced.

 

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Another possibility is the Fuel pump, you can check the pressure at the filter.
Also with that many miles the cat converter could be getting plugged up.

 

maybe a vacuum leak, throw a gauge oin it and see what your reading is