Hello, new forum member here looking for some insight on an issue I've been having.

So about six months ago I bought a 2000 Civic ex 5-speed sedan with 173k miles on it. When I got the car the temp gauge seemed to be low and the idle fluctuated some. Ended up being that the thermostat was stuck slightly open. Fixed that and hoped that would be my only issue. Unfortunately that was not the case. The car seemed to be lacking power below 3500 rpm but not enough to really affect daily driving. I figured a basic tune up might be in order so I replaced the fuel filter, did new NGK spark plugs and wires, and some fresh oil. Issue was still there just maybe slightly better. I'm now at 180k and its only gotten worse especially since the weather has gotten hotter. Now the car will stall out sometimes at lights and since the beginning of this week the car has gone into "limp mode" twice not allowing me to rev past 3k, both times when I go to accelerate after stopping. It will do this for a few seconds and then out of no where start accelerating normally. I am baffled that I haven't had a check engine light thrown while this is happening since its seems like a pretty serious issue. Today I scanned for any stored codes that might not throw a light and found nothing. Tested the primary O2 with a scan tool and all seems within spec. Also reset the ECU just for ***** and giggles. The car does have a 2.5 inch cat-back exhaust and a short-ram intake although the low rpm loss of power was present before these mods. The car also idles steady at about 700 rpm.

If anybody has any insight or has dealt with a similar issue feel free to let me know what fixed your problem, it would be greatly appreciated.

Thanks,
-Brian