Earlier this year while doing my normal tune-up, I replaced the spark plugs with a set of Bosch WR7DC plugs. I have used them for years with no problems. Lately, I had been experiencing a driveability (I want to use the word, problem, but it was not an identifiable problem) issue. The car would feel like it was sagging on acceleration, and while the idle was not erratic, it was not rock steady either. The plugs have been in the car less than 3000 miles.

This morning I pulled the plugs, and 3 of the 4 plugs had experienced seal failure. The seal between the plug body and the insulator was leaking. There was strong evidence of combustion gasses on the insulator, and a slightly oily residue. The color of the plugs was spot on, and no deposits were evident (I only burn Chevron 93 octane with Techron).

I replaced the plugs with a new set of NGK BPR6ES plugs, and took it for a test run. The idle is rock steady, and there is no sag on hard acceleration.

I just wanted everyone to be watchful for this problem. The packages that the Bosch plugs came in was marked Made in Brazil.