2001 lb7 6 speed new injecters at 107,000 now has 235,000 seem to run fine down the road but sounds like a lope tune at idle and has no tune on it any ideas on what problem is?

If i had to guess i would say you have an issue with one or more of your injectors.

I would look at the fuel pressure regulator on the back of the cp3 if it's 235,000 is a lot of miles on a fpr

If its the fpr when he monitors fuel pressure then he should get an irratic reading when it idles like this then right??

Im having the same problem with my 2001 lb7 246,000 on it. At idle, it tends to fluctuate idle by about 50 RPMs. If you replace you FPR, post the results.

Im considering buying one and seeing what it does to help.

I had the same thing happen with mine! Does the exhaust smell like unburnt diesle and strong enough to burn your eyes? Sound like it has a mad cam in it? Is it cold there?

I had a customer with the same exact problem. I have replaced the FPR's before for somewhat identical symptoms with positive results in Cummins and Dmax trucks. All was well afterward in all but 1. On this specific isolated LB7 case Im describing, the rail pressure would hang up at 12K+/- for a few minutes and fall down to the normal 4-5k @idle IIRC. It would do it hot or cold and at no particular time, completely random. Balance rates and fuel return were all acceptable and delivery pressures etc checked to be w/in spec. The truck is scheduled to come back to me soon for some other work, but the trouble has never been repaired. It is a work truck so the customer couldnt let me keep it for longer than a day or so, definitely not the time I needed to test it and diagnose further. I too am curious to know what your findings are;).

I had a customer with the same exact problem. I have replaced the FPR's before for somewhat identical symptoms with positive results in Cummins and Dmax trucks. All was well afterward in all but 1. On this specific isolated LB7 case Im describing, the rail pressure would hang up at 12K+/- for a few minutes and fall down to the normal 4-5k @idle IIRC. It would do it hot or cold and at no particular time, completely random. Balance rates and fuel return were all acceptable and delivery pressures etc checked to be w/in spec. The truck is scheduled to come back to me soon for some other work, but the trouble has never been repaired. It is a work truck so the customer couldnt let me keep it for longer than a day or so, definitely not the time I needed to test it and diagnose further. I too am curious to know what your findings are;).


Would this influx of 12k happen multiple times? The problem Im having (and it sounds like the others also) is a rough idle around 50 rpms +/- fluctuation. An increase of 12k would bump the idle up quite a bit, correct?

Would this influx of 12k happen multiple times? The problem Im having (and it sounds like the others also) is a rough idle around 50 rpms +/- fluctuation. An increase of 12k would bump the idle up quite a bit, correct?
Yes sir. The truck I had would actually rock slightly from the rapid surge in idle. The thing sounded like a low compression, retarded timed sled pulling truck! It did not happen every time either. The cust could start the truck a dozen times w/o incident. Im thinking something is causing a loss of signal to the FPR on that truck but that could take a while to find you know. If you unplug the FPR the rail pressure goes to max. psi b/c it cycles open by default.

So you've had success with replacing the FPR on multiple trucks? What mileage roughly were they replaced at? I think im going to break down and buy one, install, and see what happens. Then I just have to figure out my P0093 error code and ill be set!

So you've had success with replacing the FPR on multiple trucks? What mileage roughly were they replaced at? I think im going to break down and buy one, install, and see what happens. Then I just have to figure out my P0093 error code and ill be set!
The lowest mileage truck I know for certain was a Cummins at ~60k, but it was an 04 I think, about 4 or 5 years old at the time. The Duramax trucks were all over 100K. Most trucks around my area aren't over 200K. I also recall most of them not being LB7's, but LLY's and an LBZ for an upgraded 1 due to suspect conditions. I have only replaced 2 (IIRC) LB7's besides the troublesome 1 I was describing earlier. I dont want to make it sound like that is your issue for certain w/o testing it. I am not an advocate of replacing w/o testing 1st. If your doing it yourself though, you can save on the labor atleast. Good luck with it.:)

I also want to add, not all of these trucks were exhibiting the loping idle scenario. I had some start and idle really rough for a few seconds and either stall or continue to idle rough for a few minutes. Others would cut back on fuel by hanging up resulting in low rail psi or get hung up supplying too much pressure, kind of like that LB7. I often replace the FPR with a modified unit from Wicked or II along with the Arson or Bag-of-Parts kits for performance applications.

thanks for the info guys could anybody tell me what pressure is supposed to be at cp3 pump and what is normal for injector balance rate also price for fuel pressure regulator thanks.