Results 1 to 10 of 24

Thread: Lly duramax runs good when cold but runs and idles rough when engine warmed up

Hybrid View

Previous Post Previous Post   Next Post Next Post
  1. #1
    Junior Member
    Join Date
    May 2017
    Posts
    10

    Default

    Quote Originally Posted by bronson1376 View Post
    I have replaced the ficm with a brand new gm unit, also I wouldn't order a injector on balance rates alone. You need to do a fuel return test on the injectors because I have seen the injector before or after on some trucks be causing the problem with the balance rate on another due to the injectors being on the same rail. The test isn't hard and you can find plenty of info on how across the internet. My opinion is stay away from Pensacola diesel, I have used them twice and the injectors tend to not be the best remanufactured and no help from them when needed on warranty. I did replace my alternator but haven't driven my truck much, but seems so far to be idling smoother, but still when it's up to temp I can't any balance rates to come up. Might just be the weather right now making the idle smoother or what not, but to early to tell until I drive it more. Also one more thing I can think of that might be both our problems is the fuel pressure plug on the back of the driver side fuel rail, I just remembered I had a issue with the race plug sealing when installed at one point so I might try to test that return as well and see if maybe I have a slight leak causing fuel pressure problems at idle and what not. If I get time to test I'll let ya know the results. I do remember the race plug I installed being a cheaper brand so maybe I'll order a ppe and see if it seals better. Also another thing to check would be the wiring to the injectors to make sure they are getting good contact, gm sells a updated injector plug kit for the front in driver side and rear on passenger that are at a 90 so the wires don't break, might check that but mine has already been done
    Any luck?
    I read on another forum that some one replaced the nsbu switch .

  2. #2
    Junior Member
    Join Date
    Apr 2013
    Posts
    24

    Default

    Quote Originally Posted by thunderhead View Post
    Any luck?
    I read on another forum that some one replaced the nsbu switch .
    No luck yet, seemed to not idle as smooth as the other day but wasn't necessarily rough... to haven't had time to check the returns on the fuel rail plug due to getting my race car ready for the races but hopefully during this week I'll get the time to check. I haven't replaces the neutral switch but can't really see how that would cause idle issues but still have shifting and such ok
    Bronson

  3. #3
    Junior Member
    Join Date
    May 2017
    Posts
    10

    Default

    Quote Originally Posted by bronson1376 View Post
    No luck yet, seemed to not idle as smooth as the other day but wasn't necessarily rough... to haven't had time to check the returns on the fuel rail plug due to getting my race car ready for the races but hopefully during this week I'll get the time to check. I haven't replaces the neutral switch but can't really see how that would cause idle issues but still have shifting and such ok
    Well my Desired turbo charger vain position is 88 and my turbo charger position is 29 ? its jumping all over the place and when it really lops bad i can here it through the air cleaner like my EGR is opening up . And thats all over the place also . And i know am getting barometric pressure code . This all at idle warm .? Isn't the EGR closed at idle ?
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	TURBO CHARGE.jpg 
Views:	374 
Size:	723.9 KB 
ID:	21091  

  4. #4
    Junior Member
    Join Date
    Apr 2013
    Posts
    24

    Default

    Quote Originally Posted by thunderhead View Post
    Well my Desired turbo charger vain position is 88 and my turbo charger position is 29 ? its jumping all over the place and when it really lops bad i can here it through the air cleaner like my EGR is opening up . And thats all over the place also . And i know am getting barometric pressure code . This all at idle warm .? Isn't the EGR closed at idle ?
    I'm not sure if the egr is supposed to be closed during idle but mine is fully deleted, but now that you mentioned it, I did have turbo vane position sensor codes awhile back before the lope started that I kept clearing and called turbo manufacturer and told them and then they kinda stopped coming up, maybe for you a bad barometric pressure sensor.... I never thought my vane control solenoid for my turbo could be bad due to my turbo only having a couple thousand miles when I was getting the codes, and I don't beat on my truck I drive it like a baby, but I guess anything is possible... tomorrow I will use the Snapon scanner and monitor the commanded versus actual vane position and let you know, my truck was idling Lopey again today so maybe that will give me something else to look into... also even with a new alternator noticed voltage at idle would randomly drop off still then come back up.... possible bad alternator from napa, will order another as well and see if that stops
    Bronson

Similar Threads

  1. Replies: 1
    Last Post: July 6th, 2013, 11:44 AM
  2. Went from hot weather to extreme cold not truck runs like crap
    By andysc3 in forum Custom Operating Systems
    Replies: 3
    Last Post: April 11th, 2013, 04:18 PM
  3. EGR Deleted 6.7L Runs very rough when cold
    By Mitco39 in forum Cummins 6.7L
    Replies: 18
    Last Post: March 29th, 2012, 05:27 PM
  4. Replies: 6
    Last Post: July 14th, 2011, 03:25 PM
  5. Car tuned, runs great, idles like stock. Turn on A/C= :-(
    By ArKay99 in forum General (Petrol, Gas, Ethanol)
    Replies: 2
    Last Post: June 14th, 2005, 04:15 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •