1998 Ford F-150 Rough Idle & Missing on 2 cylinders

GREYHAIR

MEMBER
1998 FORD F-150
V8
2WD
AUTOMATIC
277,660 MILES

About 1,000 miles ago CE light came on. Codes said 401 and 408 for EGR and 301 and 308 for cylinder misfires. Replaced ALL plugs, plug wires and fuel injectors (injectors were original). After clearing codes same codes returned within 20 miles. Replaced both coil packs. Same result. Replaced in line fuel filter and Fuel Pressure Regulator valve. Same results. Here is what is wrong. The vehicle has a rough idle, runs fine when accelerating, runs rough between 35 and 55, and runs fine over that. The CE light has gone out, but I'm sure it's just burned out since the same codes still appear. Help?

1 Reply

KEVIN12881

MEMBER
336 POSTS

You have fixed and checked most of these, but these are all I have. I hope one of the helps. Missing at idle speed. 1) Spark plugs faulty or not gapped properly. 2) faulty spark plug wires. 3) wet or damaged distributer. 4) short circuits in ignition, coil(s) or spark plug wires. 5) Sticky or faulty emissions systems. 6) Clogged fuel filter or foreign matter in fuel. 7) Vacuum leaks at intake manifold or plenum or hose connections 8) incorrect idle speed or idle mixture. 9) low or uneven cylinder compression. 10) Clogged or dirty fuel injectors. 11) Leaky EGR valve