Engine hunting LMM

[Shopdog]

New issue with our fleet of Duramax. We now have a truck that has a hunting problem at idle in gear. We have had several with fuel pump failures, lots of EGR valve issues due to the high idle time. Does anyone have any experience with this condition?

 

[THEFERMANATOR]

Scan actual VS desired fuel rail pressure and see how much the actual varies from desired.

 

[WarWagon]

If it's the FPR (common) here is an idea and more discussion:
http://www.thetruckstop.us/forum/threads/lly-fpr-install.30835/

 

[Shopdog]

Truck has been on the road now with almost a 1000 miles put on it and almost 100 hours of run time. We were able to duplicate the condition only once. When it was actively hunting the FPR was reasonably stable, only fluctuating by no more than 100 psi. If it was the FPR , I would expect to see more than that.

 

[THEFERMANATOR]

another thing i have seen on an lly was a bad connection at the coolant temp sensor. otherwise it sounds like you need to check the injector return rates.

 

[Shopdog]

another thing i have seen on an lly was a bad connection at the coolant temp sensor. otherwise it sounds like you need to check the injector return rates.

Ok, will try and get that soon, thank you.

 

[tanman_2006]

I'd be adding lift pumps, prefilters, and egr deletes to those trucks...