Jerkiness at very low speed

[Big T]

I tried to do a search and the other topics that I found just dont fit my problem.
Here is what I have. More often when it is cold but sometimes when warm I "feather" the brake as I move forward or backwards the truck surges and the idle us uneven. It feels as if the brake rotars are warrped but this problem is only at very slow speeds (less that 5 mph)and never at greater speeds. Again this doesnt always happen but is becoming more frequent. Does anybody have any ideas or the same type of problem. I have a 04.5 with about 20,000 miles on it.

[red500ss]

Talked to a guy yesterday with the EXACT same "problem". He was told it was the way the turbo operates at low rpms, and causes surging. He attributed it to a change in the turbo design and programming and thus is not a characteristic of earlier duramax's.

Hope that helps

Tim

[Jackmchome]

Been there, done that. Your fuel pressure regulator is bad. That is to say it was bad in a LB7

[madmatt]

does it do it at idle? have you ever changed your fuel filter?

[Big T]

Yes is does it at idle and in park. I have not changed the fuel filter yet.

[madmatt]

it's probably your FPR like stated above.

[Chevy2DMAX]

I had my LLY in the shop a couple of months ago for the low speed surging. Was told there was no fix at the time.

[SmokeyMax]

Mines doing it. From previous experiences w/ my LB7 with the california smog crap...I will bet my bottom dollar that the egr pump is causing an irregularity in something causing the surge. My old egr pump went out and it sounded like an air compressor running. You'd be surprised how much is going with that thing and I think it only runs at idle?

[Big T]

Thanks for the help. I tried a new fuel filter no change so I took it in and I was told that there was some upgraded computer software, They updated the computer and it solved 85%-95% of my problem smile.gif .

[dmax lover]

There is a reflash that lists that it deals with surging on the lly.

jeff