I'll start by saying this isn't a critical situation, just something I'm a bit curious about. 91 Civic LX, stock since I've had it. No codes. But my car seems to drop spark in one cylinder when I decelerate under the faintest touch of throttle, in gear, literally like 1-5% throttle. I have an open stainless header at the moment, so you can hear the putter, and it pops and crackles like the fuel in that cylinder isn't getting burned. Idle isn't PERFECT but it's definitely acceptable. Absolutely no hesitation or sputter on acceleration, or 0 throttle deceleration. Like I said. The car is 100% drivable and doesn't misbehave, just thought this was a little strange. And figured I'd ask. New plugs, and dizzy cap. The car did the same thing before though. New wires might do the trick? Coil heading out? I figured if it was a rich condition there would be more issues across all cylinders. In free rev it only pops if I blip around 5000 rpms which I figured was pretty normal.

 

Sounds like a valve issue, pops and putters in the exhaust are usually caused by burnt exhaust valves. Its and older car and high mileage can cause deposits on the back side of the valves to keep it from seating properly. The fact that you hear it out of the exhaust says it's an exhaust valve. I believe your running dpfi on the throttle body, i doubt that it would be a fueling issue because the car would run like crap and have a cel on.

 

I also failed to mention that It has a rebuilt long block in it with about 2,200 miles on it. Yes it's DPFI. I was having an issue with a spark plug wire popping out of the well. My spark plug wasn't very tight. I tightened it down, that fixed that problem. That was about two weeks ago and then this weird misfire issue. I'm checking to see if it needs to be tightened down again right now.

 

I would double check compression. If it's fine then swap the coil with a new one.

 

Found the problem and it'll be fixed soon, problem got worse and more frequent throughout the rev range, and culminated in no spark at all on No.3 until heavy throttle. Bought a replacement distributor that came less a cap and rotor, I pulled apart the old diz to transplant said parts, and discovered a cracked, charred, and pitted rotor. I can't imagine it would be anything else. Points look alright.