Kia Sportage started normally as usual this morning but the engine was running rough immediately from the get go. I surmised it was a missing cylinder but no CEL showed up. Probably not an injector so I drove her off to work and after 15 minutes she ran smooth. In the evening on my way back home, she ran rough right from the start. I had dinner and waited 2 hours for the engine to cool down. Spark plugs were the main suspect. They are Denso iridiums, 8 years old and 40,000 miles in them. What I found was some engine oil in the 2nd spark plug tube, and the lower lip of the high tension connector rubber was wet with this oil. All 4 spark plugs looked OK at the center and side electrodes.
The unwanted oil was cleaned out, spark plugs reinstalled, and no more rough running engine. I was curious about how the oil in the spark plug tube was shorting out the high voltage. Isn't oil a nonconductor of electricity? I recall transformer oil is used for electrical transmission transformers, but perhaps transformer oil is a special mix?
I wiped some of my engine oil from the dipstick onto a plastic bottle cap but my digital multimeter showed infinite resistance through that oil even with the probes only 1 mm away from each other. I could only surmise that the oil was conducting electricity only when it was in a high voltage field.
The unwanted oil was cleaned out, spark plugs reinstalled, and no more rough running engine. I was curious about how the oil in the spark plug tube was shorting out the high voltage. Isn't oil a nonconductor of electricity? I recall transformer oil is used for electrical transmission transformers, but perhaps transformer oil is a special mix?
I wiped some of my engine oil from the dipstick onto a plastic bottle cap but my digital multimeter showed infinite resistance through that oil even with the probes only 1 mm away from each other. I could only surmise that the oil was conducting electricity only when it was in a high voltage field.
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