Are you having symptoms of a bad Glow Plug like hard starting or an uneven idle after you do start that lasts for minute or so and goes away?

My Glow Plug light dissapeared completely for the most part of a year but I had no symptoms of a bad plug so I knew they were working. The light came back on by itself afternearly a year of not working.

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84 300D, 82 Volvo 244Gl Diesel