MY 2001 PSD 7.3 STARTED MISSING THE OTHER DAY, AND THE CHECK ENGINE LIGHT CAME ON. AFTER WARMING UP, IT RAN FINE. THIS HAD GOTTEN WORSE AS TIME WENT ON.
AFTER SOME READING ABOUT IT, I OPENED UP THE VALVE COVERS ONLY TO SEE BOTH HARNESSES WERE INDEED LOOSE. I THEN CHANGED BOTH SIDES HARNESSES AND GASKETS. WHEN I STARTED IT UP, IT RAN FINE FOR ABOUT 3 MILES, THEN THE LIGHT CAME BACK ON AND WILL NOT GO OUT. TODAY I CHANGED BOTH EXTERNAL PLUGS, TO NO AVAIL.

WHAT THE HECK?
137,000 MILES
NEW FILTERS AND OIL CHANGED ON TIME,,,ALWAYS

 

Find out what codes are being set......

 

what were the codes??

 

My mom's did something similar on her 02. You might want to change the glow plugs all the way around, that is what fixed the problem on hers.

 

Get a buzz test and a contrubrution test and see what you get...