5th gen Prelude Fuel Management question?

Question

I have a 5th gen Prelude that is running very, very rich. I'm getting terrible gas milage fouling spark plugs on startup and dumping black smoke out the tailpipe...I replaced the O2 sensors about 10k miles ago and they are very expesive so i'm hoping that isn't the problem. Could a faulty fuel pressure regular be at blame, injectors....Honda told me something about a Cam Position Sensor...I didnt want to just start throwing parts at it, anyone got ideas? Thanks

Answer 1

the first thing to do is a fuel pressure and leakdown test. you will need to take it to a shop that has the fuel pressure gauge and line fitting adaptors; its not something you can do at home.

A fuel pressure test will tell you if you have too high a fuel pressure (very unlikely but it could happen) but more importantly it will test to determine if one or more of the injectors are leaking. Essentially the engine is run during the test to check the fuel pressure then with the return line clamped off the engine is shut off and the fuel pressure is monitored. the fuel system should hold the pressure for 5 minutes. If there is a leaking injector the pressure will start drop almost immediatly. A leaking injector is the most likely cause.

the second thing to do is to monitor the oxygen sensor signal and the switching rate. If the O2 sensor is commanding a rich mixture then you have a problem of unmetered air that is causing a lean reading at the 02 sensor; that could be a leaking intake manifold gasket or a vacuum leak. If the O2 is functioning correctly, it should be giving a full lean signal to try to compensate for the overly rich mixture. If its commanding lean, then almost certainly its a fuel injector; if its commanding a normal or rich mixture then its a vacuum leak or unmetered air getting into the engine that the system is trying to compensate for.

You don't mention if the condition clears up after driving for a few minutes. If it does, then you might want to pull the dipstick and smell the oil; a leaking injector will almost always cause the cylinder walls to wash down and dilute the oil with gasoline but a flooded engine could also cause that condition. Oil diluted with gasoline will in turn cause the excess fuel to vaporize and get pulled into the engine through the PCV system so that you would have two sources of fuel that would cause an overly rich mixture. The O2 sensor would be commanding lean if this is the case. If the engine oil is contaminated with fuel, change the oil and filter then see if the condition clears up. Again, this could be caused by engine flooding or by a leaking injector. If its because the engine was flooded then the oil and filter change will fix it.

one other thougtht; if the smoke is blue and the spark plug threads are wet then you have leaking spark plug seals that are allowing oil to get pulled into the engine and the smoke is from burning oil and not from running rich. you want to make sure the gaskets for the valve cover-to-spark plug tube are not leaking.

Those are my thoughts off the top of my head. Hope that helps

Answer 2

Honda Prelude Fuel Injectors

Answer 3

check your timming and your distributor alignment. hopefully that solves the problem.