I have a 1995 Civic EX Coupe D16z6 345,000+ M/T no CEL. I have owned it for about 7-8 months, I got a muffler delete that helped me notice a misfire in the engine. It only rlly misfired when coming out of 1st a lil bit but it would get worse when driving highway after about 15-30 min it would would just misfire in between 3-4k and at about 43-4500 the power would kick back in and stop misfiring I would keep having to downshift for it to stop, let the car cool, then drive again, but it was nun serious(wouldnt misfire in city driving) but when i’d get below a half tank it would get worse. Ive replaced ignition coil, dizzy cap & rotor, sparkplugs (multiple times) MAP sensor, o2 sensor, spark plug wires, Main Relay for injectors, pump, etc. Now its so bad till after the car is nice and warm it just misfires like crazy I pull out of 1st the RPMS drop massively & i have to rev rlly high and dogshit my clutch for it not to, same with upshifting i have rev a lot while letting the clutch out. Idk wht it is and i dnt have the money to buy a new motor at the moment CAN SOMEONE HELP PLEASEE!!!!

 

CHECK THE EGR VALVE AND THE 4 COMPONENTS that work with the egr valve. Take the EGR valve off and clean all the carbon in the 2 ports as good as you can, then the carbon in the ports on the motor, but try to vacuum the carbon out of the motor while cleaning those components.

 

Z6 doesn't have EGR

 

I'm new and dont know his to use this forum but I misunderstood and thought you were talking about a 92 civic VX that you were having problems with. I didn't Even know his to reply to your message, I subscribed, I guess that way I replied. Sorry, im not real internet literate.

 

If it gets worse when you are below half a tank of gas, then it could be your fuel pump going bad. Especially since you have 345,000 miles.