I have a 2000 Cadillac Seville SLS. 32 Valve NorthStar. It is running rough and making some noise. The check engine light is on. The code is misfire on cylinder # 6 and misfire on cylinder # 6 pending. I changed the coil pack and no change. I pulled the #6 spark plug out and found that the piston is hitting the plug closing the gap. Thus the tapping noise also. I bought a shorter plug and nothing changed. this cylinder is still not firing and there is raw gas in this cylinder. Why would the piston be hitting the spark plug?

 

One of the plugs was screwed down into the aluminum head way too far. It stripped out the beveled edge. I put a Helli Coil on the plug. The piston no longer hit the plug. However the bad news. The car now smokes like a freight train. I think the valves in the head must have sustained damage during this event with the plug. Or worse even yet, the cylinder wall is scored or a ring has broken.

 

Does anyone know what would make this 2000 Cadi SLS smoke so bad? Would you say head or piston. I know that there is a series of seals and rings and if any fail, smoke is what you get. I just want to know what someone else thinks.

 

1. do a compression test

2. failing the test, i would suspect the piston has a crack or a hole and the oil is getting into the combustion chamber, therefore smoke.

3. disconnect the wire to that plug .. does the smoke go away or decrease?
with no spark, the oil would not burn, IF there is no compression on that cylinder.
If you got compression, the oil would still blow by into the exhaust manifold and still smoke.






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There is compression. Pull the spark from that cylinder and the smoke slows down but still smokes. Now the computer is showing random misfires. I am sure it is because of the oil fowling out the plugs every other stroke or something. So.... I decided to pull the head. Everything is done but the head wont come off. there appears to be two flat head bolts with shallow allen wrench fittings. they stripped when i tried to remove them. Damn my luck. I assume that is what is holding the head in place. Ideas?

 

Stomper. Thank you for helping out. Pulled the head and the head and piston are both shot. I am now searching for a donor motor. LOL. I have several bone yards around here and I am in high hopes of finding a good deal on a good engine. I will report my progress. I have bad luck so it will be kind of funny to watch this crazy process!!!!

 

though break .. did you find a hole/crack in the piston?
also look in the local craigslist for a wrecked car with the proper engine ..




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The piston had a place about the size of a fingernail gone on the edge. Also the first ring was blown up through the hole. Bad bad bad. I found a company here in the atl that replaces the engine. For 2200 i get a replacement engine installed with 44k miles and it comes with a six month warranty. Out of a 2004 Deville wrecked. so.... I am out 2200 but will have a 2000 model cadi with 44k on it! Not so bad I guess.