I have been having this problem for a few months now, my car was randomly misfiring. I replaced the plugs and wires but to no avail. I soon noticed that the misfiring was directly related to my heat/A.C. blower. I am also noticing that when I turn on the heat it's taking a lot of power from my car's voltage. I notice that the lights dim quite a bit. This happens even when I’m not in idle. My guess is that either my electrical system is not putting out enough volts to give steady firing or my fan is taking up too much power somehow and just giving the same effect. Is it possible to have a short somewhere? can i check this somehow?

I'll rule out plugs and wires since you replaced them, and will assume they are gapped correctly.

Your fuel filter may be plugged up. Has it been changed recently?

To me, misfiring usually means timing. Has your timing belt been replaced or are you on the original? It may have slipped a tooth or two.

Consider doing a compression test. Maybe you have a weak cylinder or vacuum leak somewhere.

I'll rule out plugs and wires since you replaced them, and will assume they are gapped correctly.

Your fuel filter may be plugged up. Has it been changed recently?

To me, misfiring usually means timing. Has your timing belt been replaced or are you on the original? It may have slipped a tooth or two.

Consider doing a compression test. Maybe you have a weak cylinder or vacuum leak somewhere.
Well, The only thing is that my car runs perfectly fine when my heat is not on. i feel like a fule filter or timing belt would cause problems regardless of wether my heat was on or not. im not an expert but it im pretty positive something with my ac/heating fans are messing with it

First check the battery voltage when engine is idling and heat is "off" ... then "on". The voltage in both cases should be 14+ volts ... and you should see no change when the heat & fans are on.

But if you do ....