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Little background on my car. It's a 95 4.6L, with a Jerry II chip, 90mm LMAF. A few months back, somehow I hit the interior light switch and left the lights on all day, ran my battery down. I got it jumped, and it blew black/brown(I know I know, you never hear anyone say brown smoke, but it wasen't a pure black color) smoke really bad for a about 10 minutes, and the idle was really rough(normaly idle's around 900rpm's in park, 700 in reverse/drive). Anyways, over the past few days, it's started to act up again. Mainly whats going on, is when I pull up to a light, my rpm's drop to around 500 and it idle's really rough, like it wants to die(and most of the time the volt meter drops). This morning I let it warm up for a bit, and I could hear rpm's fluctuate. So, I get in, and give it some gas, same thing as before, dark smoke. I know I need a new air filter, clean the MAF, and probably should put new plugs/wires/t-stat in it. Just wondering if these things could cause this, or maybe if it sounds like an oxygen sensor going bad. I can also sence a slight miss at lower rpm's(1500 to around 2200).
 

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Trumpeter Extraordinaire
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Other ideas, based on my experiences with fluctuating idle, and not in any particular order:

1. Worn/bad/faulty Idle Air Control valve
2. Possible vacuum leak
3. EGR-related issues
4. Bad oxygen sensor(s)

I take it the "Check Engine" light is NOT on....?

Here's the "Rough Idle" Symptom Flow Charts (from the 1995 PC/ED Manual):

 
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