Saw this on another board and it wasn't getting much response, i think it's a common occurrence with the civics. Some people may not know whether it's in need of just a tune up or is it something drastic causing the car to do so.

Has anybody experienced a sudden loss of mpg along with sluggish power from start and when accelerating at higher RPMs have a pulsating noise like a brush stick on a snare drum under the hood or car? It sounds like an exhaust or vacuum leak. I repl the cat conv last year, tuned up the car, repl dist + cap + rotor + plugs & wires. I don't have the tell tale signs of a blown head gasket and the check engine light isn't on. I checked the manifold exhuast to make sure no cracks and it looked good. I suspect an O2 sensor or something similar, but I figure the chk eng light comes on once that is a problem. I am at wits end on what to do and hate driving such a nice car with such poor performance. Any help is greatly appreciated. CW

 

No cel is needed when a O2 sensor is going bad. More details how long has it been doing this?