Hopefully someone can help w/ my issue. I'll give as much info as I can.

I've got a 93 DX w/ the d15. It blew up at around 200k so we installed a replacement longblock. The prior engine ran fine so we switched everything over to the new engine. We replaced timing belt, water pump, plugs, wires, cap and rotor, header gasket, intake manifold gasket, plug gaskets, valve cover gaskets and oil pan gasket. It ran fine for a little while. The problem I am having is it runs extremely rich (poor gas mpg) and sounds like it has a miss. We adjusted the valves and cleaned the IACV but it still does it. There is no CEL to help diagnose.

I know this may be a hard problem to diagnose w/out hearing the car but any info would be greatly appreciated!

 

Worn MAP sensor and Clogged O2 sensors are the main culprit to this

 

^^ Id check the o2 sensors first..Maybe an injector stuck open? But i duno if injectors fail in the "open" position

 

My car has its problem upon immediate start up. Doesn't the ECU run off a base map for the first 10 minutes. This means the O2 sensor does not come into play for a couple minutes. So if my car has a problem at first and the o2 sensor isn't being read by the ECU, wouldn't this rule out the o2 sensor being the problem?

 

bad o2 sensor or cloged air filter

 

Bad injector?, distributor, bad wires, look to the ignition side first from what you say.