Surge at 60mph+

[DILLIGAFRI]

Help Since the weather started getting cool here in RI (less than 50F) I have been getting some strange surging when trying to hold a steady speed. Seems like it's fuel on or fuel off. Trying cruise control at anything over 50 and it's a herky jerky. Not as bad when truck warms up real good but still there. Better way to describe it would be if you were winding out the trans in a low gear and let up on the pedel. Coolent sensor has been changed, motor running at 185F, lift pump working , 16" vacume at wastegate, EGR pluged, FSD relocated 2 years ago. Any ideas? Hate to think I need a IP but at 140,000 it could be possible. Truck runs great and smooth with no problems and no smoke at any speed but the jerking is new and bothers me. Could it be the boost sensor on the intake. No codes at all except for the ECR codes, 400+401 that I have had for a year

98 K1500 vin "S" EGR version All stock

[DmaxMaverick]

Your EGR codes are probably caused by vacuum loss to the EGR. Could be either a failed vacuum pump, or a failing/failed vacuum switch/valve or damaged/cracked/disconnected vacuum lines. Your codes and surging are likely related.

[DILLIGAFRI]

Surging just started in the last month. EGR has been plugged for over a year or two. I know the codes are from the egr. Wondering why the surging has started only since the cold has started.

[DmaxMaverick]

If you just "plugged" your EGR, could be a plug has loosened or eroded. Also, anytime a running issue comes up, the first thing to do is change fuel filter(s), check lift pump operation, and check for leaks.

[DILLIGAFRI]

New filters, lift pump working good, no leaks either fuel or vaccum. Turbo working no black smoke at all