Around 80 mph the 1999 2500 4x4 cummins seems to lose all pulling power. Than once it slows to 65 mph it regains all power. The odd thing is that it dosen't seem to do it all the time. I have changed fuel filter and cleaned the k&n air filter. I have watched all the gauges on every time this has happened. All in the good no changes what so ever. The best way to describe what happens is it's like the throttle and the motor stop communicating until it gets back to 65 mph. This has almost got me in several wrecks on the interstate you can imagine how fast the truck slows when you lose all power. This has got me stumped!!

 

what mods do you have

 

no mods

 

What are your gauges reading?

 

tac-2100 oil preasure-60 temp around- 180 volt-14

 

What gears do you have? Mine has 4.10's and I doubt the rev limiter will let mine go past about 80.

 

3.55

 

Check for boost leaks at your intercooler hoses.

 

You might want to look at the APPS also. Others have reported dead spots in the pedal causing similar complaints.

 

I would suspect a bad lift pump that is unable to keep up with fuel demand at higher loading.

 

80 mph?? why do u need to go that fast?? and ur only running 2100 rpm at that speed?? how much are u pulling anyhow??

 

do you have a fuel pressure gauge? if not you had better get one. if you are in fact running low on fuel pressure you will hurt the injection pump.