If you have a 88 ..the 6.9 the glow plugs are easy to change ..and about 20 bucks a piece they screw out just like a spark plug ..I spry my 7.3 ..have for over a year..just check my oil and fluids ..belts an all the stuff a Driver should do befor heading out and a shot in the air intake.. and I'm off and have you changed your fuel filter..??it can have a lot of crap in it and still run..but be low on power and hard to start,,and the block heater isn't a bad thing..is this your truck or ??