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[January 10, 2015]


I was able to make it out to the hangar today to remove the spark plugs and injectors from the engine in order to determine the root cause of the issue I was experiencing last weekend. I was greeted with a little fresh snow on the ramp.


The first thing I checked was for induction leaks around the clamps. My friend pointed out to me that most likely I would see the leak cause issues at lower power settings since there would be a larger vacuum on the system (low manifold pressure in relationship to the ambient pressure). No leaks found here.


I also checked the intake tube bolts were tight.


After I took off the plenum, I noticed the #3 injector seemed to be slightly more discolored than the other injectors at the base - you ca see the black residue buildup on the bottom of the injector clearly.


The #3 cylinder top plug definitely looked like it was running lean from it's gray/white color.


After yanking all of the plugs, I got around to removing the injector. It was tough to see, but there was a very small piece of debris in the orifice of the injector. As I was looking into all of this, I learned a lot about how engines work with lean mixtures. The one thing I didn't quite fully understand is why a lean mixture leads to higher CHT's and EGT's. Before today, I would of thought a richer mixture would lead to higher temps - more gas = hotter fire, right?? Well, as I went back and forth with a friend and also read a ton on the internet, I found out that a leaner mixture burns longer than a rich mixture. A longer burn leads to a hotter exhaust temperature, as well as more time for the heat to transfer to the cylinder head. But why does a lean mixture make the burn time longer? Simple physics - the gas molecules are further apart, so it takes more time for the combustion to occur. Simple!


I made a new carrier to keep all of the plugs and injectors separate.


Good news on the way out! Gas prices dropped 60 cents per gallon!


I researched the best way to clean the injectors. The one method that seemed to get a lot of recommendations was using carburetor cleaner to spray through the injectors, and then to run it in an ultrasonic jewelry cleaner. I used hot water and Dawn dish soap in the cleaner. It did a heck of a job cleaning the injectors!


I also picked up a Spark Plug Cleaner from Harbor freight. For less than $20, I was willing to give it a chance.


Wow! What a difference! Need I say which is the before and after cleaned plugs?


The auto plugs cleaned up a lot better than the massive electrode plugs with the pneumatic cleaner - but still a great difference. Overall, a great day. I learned a lot about how my engine works, and I found the issue with my #3 cylinder. Plus 2 new toys to boot!

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Last Modified: September 4, 2017