Okay. So. I have a 2000 civic Ex coupe. D16y8.
short ram intake
Full Greddy Racing Catback Exhaust
P2P, no tune
198k miles

recently after running completely out of gas a handful of times, my car seems to not know what the air/fuel ratio is supposed to be. Daily driving in traffic, sometimes I shift at 2k rpm, sometimes at 3k. In between 1-2, 2-3, 3-4 shifts, as soon as I press the clutch there is detonation from my exhaust. Im only curious as to why. It also intermittently boggs or leans out when accelerating, like it's getting proper fuel, & then it'll just drown itself in fuel. I've re placed the fuel filter, but I haven't inspected the pre-filter attached to the pump. Should I? It primes when I turn the key but sometimes takes 500ms, or 1.5 seconds. I'm just trying to get this straight because my car performs like absolute *** ever since I've run it out of gas. When gas was 4.78/gallon. Now I'm dealing with this. Sometimes it'll run right and I get 32 city mpg. Sometimes it acts up & will burn a gallon of gas in 20-25 miles due to the a/f mixture being inconsistent.

 

I think you mean backfire instead of detonation.

what controls or effects A/F ratio? I do agree from your description it sounds like its inconsistent. I would be suspicious of the primary O2 sensor if there is no CEL on that would suggest something else is wrong. if it's original, at near 200k it's pretty tired and may not be very accurate. that's just my guess.

other suggestions: check condition of the plugs. are they all in good condition and do they all match (brand, model but also appearance, color, wear, buildup...)? verify mechanical timing and ignition timing. get a fuel pressure gauge on it and drive around with it sticking up from under the hood so you can see if something changes when it starts acting up.

 

When I force the CEL to read the code via flash sequences, it is actually code 65- primary O2 sensor bank 1. Does the O2 sensor just need replaced, or what ? I have the stock cat with the GReddy catback exhaust.
as far as the timing; I have the belt, the ps belt, ac belt, & alternator belt, as well as the water pump. But I lack a timing gun, which is necessary.
generally, I'm absolutely positive the mechanical timing is off by a few degrees. I understand that's really not good. But I can't afford a timing gun right now.

update, I've removed my fuel pump & replaced the pre-screen attached to it, as well as installed a new Fuel pump relay.
The car has been acting like it has absolutely no fuel, sputtering, with NO acceleration. It started to straighten out yesterday. But I've yet to drive it today.
it's kinda crazy, but I know the issue is simple, & there's not going to be a catastrophic outcome. That is, if I get the timing over with. The distributor cap and rotor are next, to check