check engine light at higway speed 87 gt (Page 1/1) domer94 NOV 08, 04:31 PM ive replaced gas cap , checked every line imaginable. i can drive the back roads all day with no light. once on the higway above 70 i get it. once the car is off and back in the garage , i have no light when i take it out again Patrick NOV 08, 07:00 PM And... the stored code is... ? I'll go out on a limb and suggest it's got to do with a malfunctioning EGR solenoid.