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cooztwo
New User
May 15, 2012, 10:54 PM
Post #1 of 5
(2177 views)
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#2 Cylinder fouling
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2005 GMC Envoy 4.2L straight 6 112K miles: The engine had been burning oil for quite some time and eventually #2 cylinder burnt a valve. I changed the head with rebuilt one and its running fine except its still smoking but instead of blue, its more white/gray with a tinge of blue. I don't see it happen all the time, just on occasion. I've driven it about 150 miles since the new head and I pulled the plugs (yes, new ones) tonight. Only the #2 plug had black dry soot. The other 5 were all normal. What else i've done: compression test and all cylinders 200-195, musical coil packs, I put 30 psi in each cylinder at TDC and no evidence of leaks in radiator, intake or exhaust. When I had the head off, I imspected the piston, cylinder wall and gasket surface. Everything looked and felt fine. Is it the injector? Is it the injector? Codes: P0495 Fan speed high (got it twice) / P0128 Coolant thermostat-Coolant temperture below thermostat regulating tempterture (got it twice) / P0526 Fan speed sensor circuit
Is there a way to upload pictures?
On side note: I tried to turn the VVT actuator when I put the exhaust cam gear on the cam but I couldn't. I don't know if I should have been able to or not, the spring I could see didn't look that manly so I thought I might be able turn it. Then I saw a youtube video of a guy using vice grip to hold the gear while compressed air acutated the advance. If mine wasn't working, would it cause a burnt vavle?
Oh, another thing, since it was burning oil for so long, are the O2 sensors OK, I don't have codes and the numbers I see on my actron seem to be within limits. How about the catalytic converter? The truck did leave some black soot in the drive earlier when i had it idling for a while.
(This post was edited by cooztwo on May 15, 2012, 11:01 PM)
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cooztwo
New User
May 16, 2012, 8:16 AM
Post #2 of 5
(2105 views)
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Re: #2 Cylinder fouling
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Went out this morning and looked into the cylinder. The top of the piston looks wet. 
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 16, 2012, 8:45 AM
Post #3 of 5
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Re: #2 Cylinder fouling
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Sorry to say but I'm totally unfamiliar with this particular engine and how fueled. If fuel injected at each cylinder instead or central in throttle body that injector could be leaking down. Might even see with a fuel pressure tester that it drops pressure after it's shut down,
T
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cooztwo
New User
May 16, 2012, 11:58 AM
Post #4 of 5
(2086 views)
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Re: #2 Cylinder fouling
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Thanks for the input. I don't have a pressure tester but I did ohm the injectors just now. They are all between 13.9 and 14.2 ohms. The intake looked a little oily, more than I would have thought. I don't see how one cylinder can foul unless there is a issue with something exclusive to that cylinder. Each cylinder has its own injector attached to a rail. Each cylinder has its own coil as well.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 16, 2012, 4:08 PM
Post #5 of 5
(2072 views)
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Re: #2 Cylinder fouling
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OK - My guess is even if they ohm out right is that one is leaking and putting out too much fuel while driving by description of what plug looks like. Your vehicle but you will kill a converter as they will work too hard to eat up excessive fuel. If inclined to see without much technology swap that one with another and see if the problem follows. Make dang sure it isn't getting gas in your oil by smell or finding oil level too full!
Seeing gas as you said thru plug hole isn't good for the cylinder as way too much can wash away the oil and big troubles begin. Retired long time now but the reason straight sixes are about gone is they are long. A V8 for example is only 4 cylinders long - duh. A Jag V12 is only as long as the six on each side but look how long the hoods were/are to accommodate that............
T
(This post was edited by Tom Greenleaf on May 16, 2012, 4:10 PM)
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