HIGH HC ( 15mph- MEAS 182ppm,25mph-MEAS 72pp
What is the engine code for this Civic? Open the hood, It will be on the engine block proper, to the left of the exhaust manifold, on a small flat tab just below the cylinder head where the transmission and engine bolt together. I need that before anything else...
To put it simply, if this is a D15B7 or a D16Z6 (the two most common D-Blocks in the United States from the OBD1 era), then everyone who's talking about EGR valve operation should be ignored. Because 95% of ALL global OBD1 Honda D-blocks don't have EGR valves, or ports, or even the thought of an exhaust gas re-circulation system. 1994 is too early for EGR Honda's, and most of the up-to model year 2000 Honda D-Blocks were simple exhaust port drill holes with no valves, such as on the D16Y8 and Y7's.
Are there any modifications? Hot rod parts? If so, what. Exactly what, not "a one of these, a one of those", I need to know exactly what. Are you running a stock ECM chip? If not, what fuel MAP and who wrote it? Are you even sure the ECM is original? If it's ever been owned by a kid, the odds are slim that it's running an OEM fuel and timing MAP today. How any miles on the engine? Does it burn oil? What is the overall maintenance condition of the engine? Most recent valve adjustment? And recent major work, such as head gasket, etc?
My best guess is that you're dealing with a missing CAT (knocked out), a clogged or ineffective CAT, or simply a worn out and wiped out major rotating component in the engine (valve seals, rings, pistons, etc). If you had a complaint of a running condition, such as idle surge, stalling, no power, check engine light, etc, then you've got another issue. Fix that first and move on from there. But if all you've got is a failed emissions test with no other symptoms, you've got a bad/missing CAT, or a bad engine. Period.
The early to mid 90's Honda's are flat out the best engines designed and built by man in my opinion. The D16Z6 is one of the marvels to modern engineering. These things ran so good, for so long, everyone who owned one either forgot to take care of it, or drove it till it died. Or, raced it till it died. And now these poor D-Blocks are showing up like rats to the piper at my shop asking if "The Guru of D Series" can breathe any new life into a 250,000 to 350,000 lower ends. I had a D15B7 show it's head last week with 325,000 on it. It was actually the old engine I pulled from one of my del Sol race cars in 1997 with 150,000 on it then (in favor of a B18C) and installed it in this customer's car. Here it is, 325,000 on her today, still kicking. Original head gasket and valve seals, blowing smoke like a diesel past the valve seals and guides, yet still pulling like a freight train still getting rubber when you grab third. But there's NO WAY that 'ol 325,000 mile bird could pass emissions, than god we're in Michigan She's just too old, and too worn out.