I have had a small oil leak for awhile and haven't been able to find it yet. This issue just started a few days ago. Not sure if its related or not.

I data logged everything at startup, but then forgot to change the filename before running a log while driving. I will have to do it again this afternoon. Truck turns over and fires and just fine, then starts the loping/romping idle, hunts up and down the rpms a lil bit then settles out just fine.

I did check the reservoir and there was oil about 1-1.5 inches from the top so that shouldn't be the issue. Also checked the oil pan level and it was at the full line. I need to verify the oil level because the truck was parked nose uphill so it might have been reading a little high. Oil was just changed 2 days ago.

IIRC duty cycle went from the 14-15% range up to 28% at one point. Most of the time it was in the 18-21% range during the rough idle. Pulse width came up and was in between low to high 3ms range. RPMs were between high 5's and low 8's. Wasn't watching ICP psi much, was focusing on PW and DC.

Just weird that it starts and idles just fine at first and then the romping/loping starts in and then its back to normal.

 

When did you change the oil ? Switching to 5w40 syn oil, such as Rotella T6 will fix romping problems..

 

2 days ago, always used Delo 400. This issue just stared a few days ago when I was on the old oil, changed the oil and no difference. I wouldn't think that oil would change the issue since it starts fine...romps....then idles fine after that. Seems like I'm getting air in the system somehow and then its filling back up with oil and all is well. I dunno...I'm thinking its going to be time for injectors soon.

 

Here is a graph for Cylinder Change Rotational Velocity. Looks like #2, #4, & #5 are a little wacky. Nothing over 4%. Going to do another one later on and see if things look the same.

 

Your IPR may be sticking, IPR o-rings torn or your ICP going out.

 

ICP is brand new. Tried unplugging it before starting the truck yesterday and didn't correct the issue any...plugged it back in while romping and no change. IPR may be an issue, but it was pulled out, o-rings replaced and put back in when I did the pumps a couple months ago. I have a spare I'll take apart, clean, and R&R orings on and maybe swap out this weekend.

 

If its an auto trans , try starting it in neutral..

 

No change in the romp/lope with the truck in neutral. I got the data log this time while it was romping that I'll upload later. Next thing to try is topping off the reservoir since it was 1-1.5 inches low and seeing if that helps. It could be dropping enough that the feed for the rear HPOP is picking up air.

 

Just a little update. The previous Cylinder Change Rotational Velocity graph was done around 190* EOT IIRC. The graph below was done at 203* EOT. If it was an injector o-ring issue, wouldn't the cylinders be worse at a higher EOT since the oil is "thinner" and should be able to pass by the o-ring easier? At the very least its the same cylinders that are "out" compared to the "good" cylinders. Thoughts?

 

What CPS are you running Black or the recall Gray one ???

 

Black....I've been running the black one for probably 9 months. I don't think its CPS related since it only does it once after startup and doesn't do it again until after the truck has sat for awhile. I'm 99.9% sure there is a leak down issue with the HPOP. I just have to figure out where its at.

 

If it wasn't a sudden onset issue, I'd question your LPOP. When mine wore out the early symptom was cold romps. It ended up pogressing to dying 10 seconds after starting. It wouldn't act up once the oil was warm because warm oil flows better.

 

I was just thinking the same thing Peter just posted he just beat me to it. Do you have an Oil Pressure Guage???

 

I do not have a manual gauge...I guess that's the next thing I need to pickup. The factory gauge does not come up immediately while cranking. I did replace the LPO regulator spring not too long ago because the plug was seeping. LPO pressure definitely seems ok after running. It is running about 75% on the gauge.

 

The one thing to think about is that even if the LPOP is causing a low flow issue at startup, I still need to figure out where the oil from the HPOP Res is going....