Inherited a 90 ef hatch with d15b dpfi. Replaced alot on it just to get it in the current state. Timing belt, water pump, headgasket, throttle body gasket, thermostat, coolant fan switch, gas tank, fuel pump, main relay(have 3 on hand), and map sensor(also 2 extra). Car starts fine just has a little rough idle when cold, but I've been chasing code 5. Car has a roughish idle when i first start it, and after the CEL for code 5 appears, idle smoothes out, but i can tell it's running a little rich. I've replced all the vacuum hoses, just don't know where to go from there as far as if it's an actual mevhanical issue. I have drove it around the block a couple times abd down the street to fill it with gas, just don't know what else I'm missing.

 

Did recheck timing today and that's not the issue, will check ignition timing tomorrow. Book is kinda vague on mechanical timing but ignition timing is in there

 

Caveat: I haven't messed with a dual point in a long time. Since you did the tank/pump, what's the state of the fuel return system? I would cap off the purge system at the intake to see if anything changes.

Pretty sure it runs smoother with the code because the ECU is dumping fuel - that's what seems to happen under an O2 code, so I'll bet this is similar.

 

I'll try that today, just would figure I'd have a different code then code 5 for map.

 

Honda OBD0 is oblivious and unhelpful. You only get 20ish codes after all. Always try to think of those as pointing generally to systems, not specific components.