Car was put on high load entering highway and experienced a grinding rattling doing for a few minutes and went back to normal. Check engine light flickered and code for #6 cylinder came up. Spark plugs did need replacing and improved performance but car has lost significant torque and revs high to meet higher speeds also has small metallic sound on hard acceleration.
My car has 123 miles.
My car has an automatic transmission.
It sounds like you are experiencing a lean condition and engine pinging. The most common fault I have seen for this is when the mass air sensor causes the engine to go too lean. When you look at the scanner readings with the key in the engine off position, the mass air sensor should indicate the correct altitude you are at. I have seen them read above 10000 feet when I was at less than 100 ft in one scenario. If you see this problem it may not set a code since the mass air sensor is still within specified range for the sensor but out of range for the actual altitude. Replace the sensor if it is proven to be out of range. You can try to clean the sensor but I have not seen it fix this type of issue. It is normally necessary to just replace it.
If you decide that you need some assistance with these checks, consider contacting a certified mechanic who can diagnose your loss of power symptoms firsthand. The issue can then be addressed once the problem has been pinpointed.
Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing