Having some trouble with my 92. I've looked around on here and haven't found anything really similar. I have a couple ideas, but I'm not convinced. I have a very specific misfire/stutter situation that's been happening since about April now. Some background info on the car. Got it in 2016 was told by the PO it had a couple new parts on it. Plugs, wires, waterpump couple other odds and ends. Opti is unknown. Have a hard time believing they pulled the water pump and didn't replace/destroy opti in the process. Car currently sits at 118K. I've recently replaced the fuel filter this spring and also did the EGR valve last year. Anyway, this misfire happens at 1500 to about 1800 RPM. Low throttle situations like pulling away from a stop etc. Problem only happens after the car has been warmed up and is especially bad after cruising at a steady speed and coming to a stop such as pulling off a ramp and sitting at a red light and pulling off. Car runs like a gem out of that RPM range though. It also won't do it if you goose it from a stop. It only happens in light throttle/normal driving situations. It is especially bad between 1st and 2nd. Once the tranny dumps into 3rd or 4th it doesn't seem to do it as bad. I can hear a slight spitter/spatter through the exhaust in those gears though so it is trying to do it just not as noticeable as it is in the lower gears. I'm leaning toward the opti starting to crap out, but in my past experiences with LT cars they kind of break up through the whole RPM range and not this weirdly specific range. I checked the plug wires last night in the dark thinking one of them might be arcing, but didn't see anything. I'm almost wondering if it's a weird fuel delivery issue. The car starts hard sometimes when it is hot and if the tank is low. Fuel pump is more than likely original. I don't have any pressure readings from the pump, but it is strong enough to run the car obviously. Not really sure where to start since it doesn't drop any codes. I've checked the readout and the only thing it shows is a stored code for EGR which is why I changed the valve in the first place. Just don't want to start throwing money at it without a gameplan.

 

I would get some fuel pressure readings then. Plus a leak down test.

The reason it could be happening at low RPMs could be a leaky injector that is causing an extremely rich condition. Though, when you are turning more RPM or "goosing it" and it needs more fuel, it is not noticeable.

With very little to go on, I would start there to develop the game plan. Also doing maintenance items like a fuel filter, IAC housing clean out, Throttle body clean out etc. shouldn't be considered as throwing money at it. With such a slight problem and no codes, something silly like that can cause little anomalies. The maintenance items need to be done anyway.

 

When my coil started to fail my car did weird things like yours until it started to die and then completely die. Something else to think about is it possible that vibrations are causing one of your spark plug wires to touch a header or something else and possibly short.

 

I've cleaned the IAC and just did the fuel filter this year. Haven't taken the throttle body off yet to clean it. Was thinking about getting one of those cheapo air foil things anyway for some imaginary horsepower. I had one on my Camaro and only paid like 20 bucks lol.

 

This is what I was really suspicious of. The whole area around the coil looks kind of crispy. The boot that connects to it is definitely grimy and looks kind of dry rotted. I was hoping I might get lucky and it was loose, but it was still snug when I pushed it. Maybe this winter I'll do plugs, wires, coil, and opti. Like I said in my original post I have no idea how old that stuff is just taking the word of the PO. The car has taylor wires on it so he may very well have done the plugs and wires and not messed with the opti, which seems crazy to me.