1999 Chevrolet Suburban • 131,000 miles

We have a random misfire condition which includes an intermittent engine shudder, usually when pulling inclines under load, on the 1999 Chevy Suburban (1/2 ton, 4WD, automatic, 131,000 miles). The following services were performed on the car:

• Replaced fuel tank sending unit – 65,434 miles
• Replaced fuel pump and connector – 80,505 miles
• Replaced the fuel filter – 88,771 miles
• Complete engine tune-up (spark plugs, rotor, distributor cap, ignition wire set, PCV valve) – 92,804 miles
• Repaired faulty ground wire on the engine block
• Replaced distributor cap, rotor, wires, spark plugs, complete fuel injector assembly – 122,869 miles
• Replaced ignition coil – 130,000 miles

Nothing has helped, and now it feels like it briefly cuts in/out (literally a split-second flicker but will do it several times in a row) while driving on flat road @ 45 mph. At one point recently, the engine was misfiring badly, and I was down on power that it felt like I was braking not accelerating. I pulled over and without warning, it self-corrected and drove like a well-oiled machine. This has happened several times, but the engine self-corrects its misfire and drives fine.

I checked all the fuses, air filter, etc, but there are no apparent problems. What else should we check?

El Cheapo
June 16, 2013.

Have a pro check this, random misfires can be caused by several things an dhe needs to scan to see if any sensors are out of whack

Jun 17, 2013.