Running rich

[sparks_welding]

Hey fellows what makes a 90 302 run rich??? I'm assuming o2 sensors. On start up it idles high up to 1800 then drops down to 800-900 only on first start up when engine hasn't been run. Idles up for about 3 to 5 sec then drops. I'm getting horrible gas milage. I got on it and when i left off it was like doing a key drop popping the gas out of the mufflers lol. I also have electric fans with the stock alternator and seems not to be enough juice to run everything. Can that affect output to the ignition system???
I replaced cap rotor plugs there fine. The motor is stock all's it has is offroad h pipe and cold air and 3.73 gears. I know the gears hurt milage a little but I'm only getting about 170 miles out of a full tank:angry:.
Anyone have any ideas???

[henrod]

could be the 02 sensors bad, i know for the breif period i had mine unhooked until i found a new 02 harness mine ran very rich and didnt want to run right. with mine when i came to a stop quickly it would die sometimes, and would act like its loading up at idle. Once i put the harness on and hooked them back up, ran noticably better, and gas millage improved. I think if your alt wasnt big enough for the car it would cut out or miss under hard acceleration where the coil isnt getting enough power. I wouldnt think the alt being to small would make it run rich

o2 sensors arnt that expensive, they are around $20-25 at advance if i remember right. may could try swaping them out

[sparks_welding]

I'm guessing it's the o2 sensor also. Thanks for the response. That will be what I'm doing this weekend is probably replace them.