Yes. Any unburned fuel that escapes through the exhaust, is called Hydrocarbons(HC). I have been dealing with hydrocarbons for the State of New Jersey for as far back as 1983. A spark plug, wire, any secondary secondary ignition problam will cause a misfire and high HC's, a state failure for emissions testing. Of course a mixture that is too lean will have an incomplete combustion, causing the same problem, especially with a Mass Air Flow type of fuel injection system. The areas to look are vacuum hoses, intake manifold leaks, EGR leaks, positive crankcase ventilation system leaks, and many others. I sometimes use a tachometer, and a spray bottle to check different spots for changes in RPM's while engine is running when I spray water, or carb. Cleaner lightly in spots.
Any loose clamps in the air intake, before, but especially after the air flow sensor. A leak down test can also be used. A good visual check is first. I hope I have helped you in some small way.
I appreciate you.
Wednesday, November 18th, 2009 AT 10:48 PM