‘99 2500 rough idle

[gringocummins]

Hello, I’ve been trying to chase this rough idle issue for weeks now. My truck is a 1999 2500 with an s362, edge juice with attitude, bd 3 piece exhaust manifold, 200hp injectors (don’t know the brand, of size of holes or how many of them). I have other non power train parts but those are the ones that I can think of off the top of my head. 
 

My issue started after I put in 200hp injectors used that I bought from a reputable person and I did not get them pop tested unfortunately. I properly bled the fuel system and it started right up. I noticed immediately that it had a rough idle and stutter that was really mild that you really had to listen for. You could hear it more from the exhaust when you stood by it. Recently in the past week or two, I’ve noticed that sometimes upon start up it’ll have a higher than normal idle around 800rpms while normal is 750rpms. I’ve also randomly experienced a surging right after startup as if I lightly tap the throttle 4-6 times. When I apply any amount of throttle or if it’s under load the issue completely disappears and I have lots of power. It only happens while idling in drive, neutral or park.

 

Things I’ve tried: I’ve watched the APPS % and it doesn’t change or appear to be affecting it. Tightened all high pressure fuel lines. Removed edge box with no change. Tried pulling codes and I have none whatsoever.
 

I’m really concerned that my vp44 is starting to go and I’m not sure what to rule out next. Could it be my injectors need to be pop tested and reset? If so, what would cause that surge? Could it be a bad ground at the PCM somewhere?? I’m at my wits end and would be extremely grateful for any insight. 
 

Thank you in advance!

 

 

[Tractorman]

You will be getting more qualified responses shortly, but I think that higher horsepower injectors simply have a bigger hole which makes it harder for the ECM to control fuel at idle.  Getting the pop pressure set at a higher value will help.  Also, a valve lash adjustment may help.

 

Others will be responding soon.

 

- John

[dripley]

If itmatarted with the injector install they would be very suspect. There is truth in what @Tractorman says about the larger injectors.affecting idle. They can cause a lope also. Something a bit odd to me is the idle. Mine has idled at 800 rpm since I drove it off the lot in 2001. But I would defer to those smarter than me also. They will be along.

Edited September 4, 2020 by dripley

[gringocummins]

2 hours ago, Tractorman said:

You will be getting more qualified responses shortly, but I think that higher horsepower injectors simply have a bigger hole which makes it harder for the ECM to control fuel at idle.  Getting the pop pressure set at a higher value will help.  Also, a valve lash adjustment may help.

 

Others will be responding soon.

 

- John

Hey John, thanks for your reply. That’s what I thought originally but sometimes it’s a mild lope, sometimes it goes up to 800rpm and bounces a bit there with a hiccup usually it’s at 750 bouncing a bit lower is 735 to 760 with a mild hiccup. The surging worries me though.

 

1 hour ago, dripley said:

If itmatarted with the injector install they would be very suspect. There is truth in what @Tractorman says about the larger injectors.affecting idle. They can cause a lope also. Something a bit odd to me is the idle. Mine has idled at 800 rpm since I drove it off the lot in 2001. But I would defer to those smarter than me also. They will be along.

Thanks for your reply as well. Before the injectors it would always idle at 750 perfectly with no issues only after the injectors does it fluctuate and sound a bit rough. 
 

In regards to lope, I thought only larger cross over tubes, larger high pressure fuel lines and huge injectors will. I didn’t think 200hp would cross that threshold.

 

[dripley]

7 hours ago, gringocummins said:

Thanks for your reply as well. Before the injectors it would always idle at 750 perfectly with no issues only after the injectors does it fluctuate and sound a bit rough. 
 

In regards to lope, I thought only larger cross over tubes, larger high pressure fuel lines and huge injectors will. I didn’t think 200hp would cross that threshold.

 

My RV275's lope a little when I turn ac onm for few seconds anyway. Nothing oversized on my truck.

Before installing these unkown injectors all was good. After installing you have issues. Makes the injectors or the install suspect.