Z24 Engine stutters, loses power and charred spark plugs

[RafaelSagrero]

Good evening friends, I hope you can help me, I have a 1986 nissan 720 truck with a z24 carburetor engine. Failure started a few days ago, the engine stutters, loses power, throws black smoke and the exhaust outlet sounds like popcorn exploding there when I release the accelerator downhill.

 

Then I check the spark plugs and they are carbonized, I clean them a bit until they are like new and I and I check their gap is 0.031-0.035, it starts to work normally sometimes a couple of days and sometimes only a few hours until it fails again and when I check the plugs Spark plugs are carbonized and I repeat the process.

 

Already checked the carburettor, cleaned it and changed gaskets. The spark plugs are Champion N9YC, The salesman at the local auto parts store sold me those, I have the feeling that the problem is the type of spark plug but I don't want to make an unnecessary expense until I have some more information.

[NC85ST]

I would only use NGK’s personally. There is a difference between the intake and exhaust side plugs. I don’t remember the part numbers off hand. 

[datzenmike]

Nissan supplies them with NGK so only run NGK. BPR6ES for the intake and BPR5ES for the exhaust so the parts guy is WRONG!!!!!!. Champion were only good on '70s Dodges.

 

Do you have dual plugs per cylinder? 8 in all?

 

 

 

Check that when the engine is warmed up the choke flap is fully open. Is it???