88 LX-i loses power as it warms up...

[Chaosracer]

I have an 88 LX-i and when I start it up it has a ton of power, but as it warms up to normal operating temp it loses power and acceleration. It was fine until I replaced my stock muffler with a Cherry Bomb muffler. Could the muffler be causing it?

[HondaBoy]

i've never heard of that happening after changing a muffler. you wouldnt have happened to mess with the oxygen sensor did you? in my case, when i first start up from a cold start, it has less power than it does after about 6-10 minutes. thats depending if im taking it easy. probley all cars i've drove run with more power after they have warmed up. your car isnt overheating is it? if it's getting too hot that'll make it lose some power. the only thing i can guess after changing a muffler that makes a power loss is having too little back pressure. my friend had no mufflers on his kia. it had all top end power but nothing less than shitty power on the bottom. he got a generic turbo muffler and has power at the bottom and top now. go figure. have you ever changed out your ignition system? i have noticed it doesnt lose power when it gets hot now that i've changed the cap, rotor, plugs, 8.0mm wires and an MSD coil. it wasnt until i changed my coil that it did the best. hope you can find your problem.