Originally Posted by Name4004

I've got a 98 civic d14a4. Not long ago I had a terrible exhaust leak, so I changed the whole stock system, cuz It was all rusted out, replaced the cat temporary with a resonator, cuz I didn't have the proper cat at the time. So I drove the car for 2-3 weeks and a strange problem occured. On a cold start the rpms are a little high and surging between 1.6-1.7 and there is white smoke coming out of the exhaust (not much) and from what I can tell It is running rich (heavy gas smell and bad gas mileage). No CEL. Once It's warm the rpms go back to normal but smoke keeps coming out. Stuff I checked:
1. It is not coolant, doesn't smell sweet at all, smells like burnt gas
2. The car isn't overheating
3. No loss of coolant or oil, no oil or exhaust gasses in the radiator, no white mixture of oil and coolant on the oil cap. No air in the cooling system as well. Doesn't misfire and no performance issues whatsoever. 95% sure It's not a headgasket, but I don't have a pressure tester..
4. It's not condensation, because It keeps coming out even tho the car is at operating temp.

I'm suspecting a problem with the air/fuel mixture. Spark plugs need to be replaced soon so I might change the O2 sensor as well. The smoke is white, but when running rich It should be black-ish and that confuses me. Haven't put the cat back on yet, but in any case scenario, white smoke shouldn't come out, catless or not. Any tips will be highly appreciated. Btw the car is absolutely stock.