Rep Power: 705

i cant seen to pass emissions
i tryed 4 times
put a new cat on
new o2
timming
it passes on all areas but fails on the CO% by double the limit
any thoughts
maybe to rich/lean
i have 91 civic with stock SOHC ZC

 
Rep Power: 802

high Carbon monoxide would indicate the you are running rich. This would mean any factor that would cause less oxygen to be present or more fuel. Obviously fuel is a more common factor to go wrong rather then oxygen. I would test the following:

Fuel system
Ignition timing (you said you have already done), I would also check ignition components.



Fuel system:
-Fuel pressure regulator (simply unplug and if engine rpm increases then it works)
-system fuel pressure (need a gauge hooked up to the service port located on the top of the fuel filter located on the firewall)
-injector noid test (need a noid light to see if injectors are firing right and proper signal, basically a jumper light hooked up to the p2 injector plug)
-injector voltage (signal from computer)
-injector resistance (injector carries proper internal resistance to operate properly)


If all is within proper operating specs. i would then turn to using a lab scope on other vital sensors that play a key role in fuel delivery.

Personally you can only tackle the ordeal for so long until specialized equipment is neccissary to diagnos these kinds of problems. I had a similar issue at one time and swapped the engine out because i had a spare. I took apart the old one and there is a bent connecting rod. My car was burning tonnes of oil and i thought that it was the usual honda ordeal, until after changing valve seals and a few other things when i began questioning myself.
This is just an example of how emmissions diagnostics can be unpredictable sometimes.

Good luck

 
Rep Power: 705

Thank You very much for the tips