Some strange issues
 

I have a 92 civic DX with the 1.5 sohc. I have 2 strange issues. I know the 92 d15b has the oil dipstick going between the exhaust manifold however my engine has it by the timing cover so am I right in a assuming that someone swapped in a newer engine? If so what year could that d15b come from cause 96 and newer civics only had the 1.6 never had a 1.5. Second issue is when the engine is cold it will idle at like 1800 rpm and when the engine is hot it will idle around 400. Its a 5 speed with a cold air intake