95' GMC Jimmy Engine miss, help please!

I got a 4.3 L 1995 GMC Jimmy, and lately i have noticed problems with my car. When in park and ideling in drive, the rpm's fluctuate a lot and the
engine misses. Also, when driving on a highway at about 60 mph, I notice the same problems. I have recently removed the EGR valve, cleaned it out and replaced it; that did not work. Next I bought spark plugs and replaced them all, still that did not solve the problem. Also, I scanned it with the ODB II and I got the message "scan successful, no problem codes available" 14,000 miles ago, i had the same kind of problems so I replaced the fuel injector and that solved the problem. It ran good until now. Any responses would be greatly appreciated. Thank You.
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Top-posting agan...
If you get a chance, (with the engine OFF) take the air intake off the throttle body and take a look down inside. You will have to open the butterfly valve all the way. Look for changes in color on the inner surface of the intake. If there are any really clean areas (bare metal) in the normally sooty or slightly greasy coloring, you will most likely have a fuel management problem (leaky diaphram on the regulator). Fuel is leaking and cleaning off the intake, and the engine is not expecting to have this fuel.
I'm sure there are others here that can describe the problem in much more detail. Especially what parts are affected.
On Sun, 17 Apr 2005 19:30:00 GMT, "David via CarKB.com"

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On Sun, 17 Apr 2005 19:30:00 GMT, someone posing as David via CarKB.com donned fireproof bloomers and chiseled in the wall:

Just a thought, if you've still got that puppy, you might have a fouled up cat or an O2 sensor (but not enought to send a code).
At idle, what do you smell from the exhaust? Does is smell normal?
I miss my '95 Jimmy. I don't miss the injector spider. :)
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Thank you. Yes, I sometimes smell sulfur (rotten egg smell) It was a lot worse before I had it fixed last time.
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On Mon, 18 Apr 2005 19:46:37 +0000, dave hoffman via CarKB.com donned fireproof underwear and scratched on the wall:

Good luck with it then. You might check out the S-Series forum at: http://forums.s-series.org/viewforum.php?f  - they have a ton of stuff on the 4.3L.
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Just to let you guys know, I removed my Oxygen sensor to see if it was bad, and when i put it back on the car would not start. I later went out and bought a new sensor and replaced it. After installing it, it still didn't start. I didn't think that the O2 sensor could possibly cause this. Turns out, it was the coil cap on the distributor that caused the car not to start. The cap was bad, all corroded and rotten. After buying a new one, my car runs great and I am looking forward to getting better gas mileage. Thank you all for your help.
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