uneven RPM's at idle

[kslayton]

After installing my DD2's a few weeks ago my truck has been fluctuating +/- 50 RPM's at idle. The tach used to be rock steady at idle but now it can't sit still. The truck seems to idle smooth and sounds fine so I am wondering if this is normal with larger injectors or if maybe I messed up during the install? Also, at first the acceleration was smooth throughout the powerband but now it seems to have a hesitation( or shudder) at WOT in 5th gear. WOT 1st thru 4th gears

is smooth. I'm waiting on a tapped banjo bolt before I can install my FP gauge. Could these be symptoms of lift pump failure or something else ? All opinions welcomed





Thanks,



Kevin

 

[DEZLPWR]

That is normal.....

Same thing happened when my DDII's went in... . I can't explain why the larger injectors cause the fluctuating idle, but they do. I wouldn't worry about it. Anybody out there want to explain why they do this??

 

[zman]

same here...

Mine did the same thing after installing DD2's, but I already had a slightly rough idle. The DD2's made it worse though. I talked with Lawrence at DD and he said that it was one of two things. Either one of the injectors/injector tubes is not aligned properly with each other causing a minor fuel leak, or the end of one of the injector tubes is slightly damaged causing it not to seal properly on the injector side. After hearing this, I pulled all of the tubes and inspected them and found one that looked suspect, so I replaced it, but it didn't help. Sooo, I'm not sure what my idle problem is at this point. I think there is still a possiblity that one of the injectors isn't perfectly flow matched with the others. I can hear the unevenness of the idle on mine, so I'll probably take it into a qualified diesel injection shop to have them look things over. Good luck...



Steve

 

[Cummins4Life]

My truck is stock and it's idle rpm's fluctuate the same way you described. I dont know what the cause is but I would like to find out. Oo.

 

[Mojo293]

Mine does the same thing but not all the time. It's something only I can sense, you know when your truck 'feels' different at idle. Usually it's after a long period of driving. I noticed it several months after injector install so that's not the problem. I thought it could be the injection pump. But why not all the time?

 

[BILLUA]

I also just installed DD2's and noted the same fluctuations. . It seems to be common with the DD2's and power edge. I didn't notice the fluctuations at idle with the DD1's. .

I wonder if the anyone with the DDTT module and DD2's can let us know if they get the same idle fluctuations. I know the timing of the Power Edge is a little more agressive than the DD true torque and maybe this manifests itself at idle with the DD2's.



JMHO



Bill

 

[Steve M]

Mine does it too and it's stock. I have to believe it's the way the tach displays the information from the CPS-PCM and finally the instument panel. It doesn't display 760rpm. Only 750, 775, 800 etc. So if it's idling at around 750-760rpm, it'll read 750,775,750 intermittantly. Just speculation but I work with encoders on elevator equipment that do the same thing and it's a good possibility with our trucks too since they have electronic speedos and tachs.

 

[Sean Flanagan]

My truck has had a rough idle for almost 50k miles now. You can feel and hear the thing miss. It still runs great. The wierd thing is, it only does it when then engine is good and warm. All the injectors and connector tubes were replaced by the dealer.

 

[Snow man]

My truck idles rock steady with dd3's,it used to burble and stall when you dropped it on gear before i had it reflashed. all is good now. My dad's 01 idles a little uneven once in a while,with dd2's,but its smooth 99% of the time.

 

[fj40charles]

Mine tach fluctuated at idle when it was stock. Same results with DD1's and now with DD2's. I don't believe it is an injector problem, but rather the way the tach is "reporting" the rpm's.

Engine sounds very smooth to the ear.



Charles

 

[High Voltage]

Iam runing with the DDTTPM and DD2's and the idle is very smooth. The only time the idle was bad was after the install of the DD'2 but a few runs at WOT took care of that.



Hutch

 

[SEmerson]

mine got a little uneven after my new vp44.

 

[kslayton]

Thanks guys,

At least I know mine isn't the only one . Does anyone have the problem of acceleration not being smooth in 5th gear WOT? It was very smooth for the first couple of days but now it's sort of jerky( for lack of a better word).



Kevin