I am new to the forum as well as a newbie to diesel pickups. I have a 2001 2500HD 4x4 CrewCab with the 6.6L Duramax. I have noticed that while I am driving the rig there seems to be a feeling that the brakes were depressed and slowed the truck then it stops and it will do this all the time driving. If I set cruise control than it does great with no feeling of engine slowing and letting off.

I have searched the forums but cant seem to find anything.

2001 GMC 2500HD 4x4 CC 6.6L 250K miles. No modifications that I am aware of

 

Any smoke ? trans fluid levels ? any CEL ? or codes ?

 

No smoke, fluid levels are good, no codes or check engine light. Changed the oil and fuel filter.

 

Need to get in and scan it ... get the Fuel pressures... sounds like a starvation issue possibly ...

 

Can I get a scanner or do I need to take to diesel repair shop?

 

Tech two or autoengenuity

 

Air Filter, had this happen to me recently with the pickup I just bought. Changed the air filter and it mostly went away, I need to change my fuel filter and see if it completely goes away.

 

A shop or EFI live will be able to scan it as well from my understanding ...

And by all manes look over the intake as well .. also .. might look into getting exhause checked for flow as well ..... if the Catalist is plugged it can Back pressure, strangling the engine

 

I believe that year did not come with a CAT. but your thinking of excessive back pressure causing the engine to have to work harder is correct.

i would check fuel pressure, fuel filter, air filter and MAF as a starting point

 

Plugged muffler of baffels that have come apart inside ..