08 343 Excalibur misfire

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   08 343 excalibur motor with 1100 well maintained hours. No salt use ever. 
 Recently having hesitation and rough idle with black smoke at idle. 
Just did a PM which included new fuel filters, recommended plugs, cap and rotor, plug wires, oil and filter change. (even bought a second cap to try to be sure I didn't get a bad one). 
Still having same problem and after going one by one on the new spark plugs (replacing with a new one to be sure I didn't get a bad one) I find one cylinder with a white basically looks un used porcelain. Other plugs are light black to dark brown. Apparently that cylinder was on the compression stroke when Removed the plug as I got a strong hiss of air when I loosened the plug. (engine hadn't been run since Sunday (24 hours). I don't have a compression tester.
 Small dash temp gauge stopped working around same time but digital display in tach reads normal temp when warmed up (150-160). Dealer says as long as digital gauge works that it is not the problem. 
 Has anyone ever had an injector go bad on one of these? 
No codes stored when engine checked (not running). 
Anything else?  I'm stumped and took it to the dealer ..Sadly hourly rate is near $150

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shagit Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: March-14-2008 Location: United States Status: Offline Points: 301	Post Options Post Reply Quote shagit Report Post Thanks(0) Quote Reply Topic: 08 343 Excalibur misfire Posted: October-22-2019 at 3:42pm
	08 343 excalibur motor with 1100 well maintained hours. No salt use ever. Recently having hesitation and rough idle with black smoke at idle. Just did a PM which included new fuel filters, recommended plugs, cap and rotor, plug wires, oil and filter change. (even bought a second cap to try to be sure I didn't get a bad one). Still having same problem and after going one by one on the new spark plugs (replacing with a new one to be sure I didn't get a bad one) I find one cylinder with a white basically looks un used porcelain. Other plugs are light black to dark brown. Apparently that cylinder was on the compression stroke when Removed the plug as I got a strong hiss of air when I loosened the plug. (engine hadn't been run since Sunday (24 hours). I don't have a compression tester. Small dash temp gauge stopped working around same time but digital display in tach reads normal temp when warmed up (150-160). Dealer says as long as digital gauge works that it is not the problem. Has anyone ever had an injector go bad on one of these? No codes stored when engine checked (not running). Anything else? I'm stumped and took it to the dealer ..Sadly hourly rate is near $150

MrMcD Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3590	Post Options Post Reply Quote MrMcD Report Post Thanks(1) Quote Reply Posted: October-22-2019 at 4:57pm
	A compression tester is cheap, less than $50 and might tell you the problem is elsewhere. A leak Down Tester might cost a little more but would tell you if your valves are sealing properly or if your head gasket is leaking. What you might do first is listen to your Fuel Injectors as the engine is running. Take about 2' of 5/8 heater hose and put one end on the injector and the other in your ear. Listen for the fast tapping of the injector working. Listen to several of them and compare to the cylinder with your white spark plug. If it is stuck closed or not getting the electrical signal to fire the injector the bad one will be quiet. The 343 says it is port fuel injected so one injector per cylinder. Make sure the injector wire is still attached, maybe you have one broken wire clip and it is not connected. Your White spark plug is either not getting any fuel or that cylinder has a lean burn condition, not enough fuel or it is getting water/coolant washed. Either due to an intake leaking coolant or air into that cylinder or a blown head gasket. Compression check will rule out blown head gasket.

08 343 Excalibur misfire

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