Strange idle, 1000rpm to 800 up and down

[FyreDaug]

Just started today actually, when I'm sitting in neutral the car will go up and down with its idle, not all the time. After I drive it for a bit it's sometimes fine, but every now and then it bounces slightly and a whole cycle of going up and down takes about 1 second. I can tell the voltage slightly changes when it does that too (probably because of the alt getting less rotations). But even if I rev to 1500 and hold it there, it bounces from 1300-1500. Any ideas?
I've redone all my cables in the car with 4 gauge, new plugs, dist cap/rotor, batt and alt.

I searched and it came up with a couple symptoms I was having but not totally, would this be a problem with fuel filters? Ive got them both at home to put in I just havent had time yet.

EDIT: And when it goes to drop the idle it "pops" like a faint catalyst popping sound. Its not noticable inside the car, but outside you can faintly hear it. Maybe a problem with spark?

[vmoul]

It could be several things.
My own experience was that my car would fluctuate between 1000 and 3000 then it started to get stuck at 4000 and it wouldn't 'kick' down. it turned out that the hot air diaphram was leaking and the cold air intake valve needed to be replaced also the vaccumn hose in the back of the carb was disconnected and it needed some adjusting. My car also had the 'popping noise' very slightly almost as if it was missing. When it went to the repair shop they pulled a fuel sample and the fuel looked like muddy water. They dropped the tank and cleaned out the fuel system. All of this work was like 1200.00 but I couldn't replace the car for that much so I got it fixed. It runs fine now.

This may not be your problem but it is what was wrong with mine.

[FyreDaug]

Well my friend just filled up at the gas station I went to (I filled totally up) and he just put a couple bucks in today, his car is kinda having the same symptoms with the idle, but I filled up 2 days ago and this is happening today. I dont think the problem is the diaphram or a vacuum leak or anything because its more intermittent than not

[A20A1]

PCV maybe... I bypassed the rear filter and ran a large clear fram filter up front in place of the stock one.

This is more of an off idle problem/solution but Did you check the booster venturies... sometimes they stick and unstick... it's when they are loose when they cause fuel delivery problems. Do you nottice hesitation if you floor it?

[FyreDaug]

Sometimes, only during low speed, like 20kmh in 2nd. But its actually more rare than not, its studdered a couple times too

[88eyeguy]

what level was your fuel at when this started happening?

[FyreDaug]

About 60%, maybe more. It was doing it again last night with nearly no fuel left (giving myself about 40k to fill up) but not so bad. I did the PCV valve today now that I found out where it is. Hasnt done it yet today, but its intermittent I'll find out later. I've also done the front fuel filter, and I'll get around to the rear one soon because its sitting in my garage right now