Engine/Transmission (1998.5 - 2002) Surge at highway speed

[PBliss]

Last weekend we took a trip and on the way had the cruise control set at about 70 mph (just below 2000 rpm, fuel mileage test) truck would speed up like WOT and once speed was at where it was set the truck let off completely and would slow a couple mph below and cycle. I thought maybe the edge had something to do with it so I turned it to zero without any change. On the way home driving faster 80-85 mph the 'surge' was worse. I noticed that the tech would vary as much as 100 rpm. I turned off cruise and drove with pedel and same problem. I wouldn't move my foot but the truck would do the same thing. It got worse as we got closer to home several times without changing my foot the truck felt like I let off alll the way, or was WOT. If I would push the pedel WOT it would run out like normal. Today in stop and go thru town no problems. I had replaced the APPS about a year and a half ago. I have not checked for any codes anf the CEL is not on. Thanks in advance for any sugguestions

Paul

 

[Pat@BD]

Before you put your airdog on had your factory lift pump failed completely? I would try taking your edge module right out to see if that changes anything. If not it could either be an APPS or an injection pump problem.

 

[Mishkaya]

I would check for codes first, and then remove the fueling box completely to eliminate it as a problem for sure (I've seen weirder things happen). Otherwise I would suspect the apps or VP44 as stated above.

 

[PBliss]

I just checked, and no codes. Before the airdog I had a walbro pump, when I changed the factroy LP to walbro we installed a big line kit from the tank and the big line between the fuel filter and VP 44. I will try unplugging the edge compleley and see what happens. Thanks Paul