I was at Wal-Mart today and was walking back to my truck and I walked by another 03 or 04 Dodge diesel that was idling in a parking space. The idle was at a normal RPM but I noticed that the idle was loping, with a constant increase and decrease in RPM's. About every second, the idle would just barely increase, then decrease, then increase, then decrease.

Was this something wrong with his truck or something that he did to it to make it do that ?

 

My 03 has the same problem, at idel it is very inconsistant, while driving it is fine.

I took it to the dealer cause I thought an injector or something was bad and they pinned the problem as being my injector pump. it's going to take them 1-2 weeks to get the part then they have to install it. Hopefully it takes care of the issue.

 

It's normal. Mine does it especially when the weather turns cold. It also does it when I run the quad box on the higher settings. It's a bit irritating but runs fine otherwise so I'm not worrying about it (2 years and running)....

 

I have heard mine do something kind of like it in the cold winter months when first starting, but today was 86 degrees and it was loping like I breath after running a hundred yard dash. Mine never has done anything even close to this so was just wandering if his was broke or mine was missing out on something.

 

My '03 started doing it this summer. I kind of convinced myself that it must have always done it, still drove fine. Now when I start the '06 I notice immediately that this ebbing/surging idle is NOT there so the '03 had probably developed a problem .

 

I know this is in a totally different realm but the Caterpillar 793c”s with the 3516”s can sit running at low idle when its cold outside, and by the electronics increase in rpm to provide heat because the engine will not make enough at idle. Do these do something similar?

 

I would be curious to see what the desired & actual fuel rail pressure was on one of these lopey trucks

 

.....fuel control solenoid.

 

Either good or bad. When ever I see another Dodge Diesel, I usually place a piece of paper on there saying to check out DieselTruckResource or TDR.

I always like to pass on great information and people to other Diesel people.

You never know, maybe some day that guy might help you out of a problem because he read it on DTR before you did.

 

Add my truck to another one that has the odd idle. Been this way for the last 2 years. Runs fine otherwise. Does not do it with the exhaust brake on at idle.

 

They do have a cold tempeture fast idle feature. On cold mornings if you let it sit and idle it will increase the rpm to around 1200 to help warm things up. But it is smooth with no lope. I believe the posts concern is it doing it at an idle. My "03" idles smooth.

 

Mine's been doing the same for a couple of months now, with or without quad. Have been trying every possible instance to make it consitant enough to take it to the dealer but I can't reproduce it on command. Closes that I have found so far is if I add 32oz of ps and keep the tank above 1/2 full it goes away. It also seems to do it a little more when warm then when cold.

 

Might be from wet-stacking. Even when it's 100 degrees outside, 10 minutes of idling has the pre-turbo egt's under 220 degrees, way too cold to burn all that fuel off. High idle it at 1,200rpm or so to keep the heat up in the cylinders.

 

You misunderstand, I am saying that it would be interesting to read the values on a scan tool of what the desired and actual rail pressure is while the engine is loping at idle. It's common on the Duramax to have bad pressure regulator causing a lopey idle because the actual rail pressure varies when it should be steady at idle. Not sure if the cummins is set up the same though.

 

....no misunderstanding Wild one. Depending on how much of an idle fluctuation were talking about here, I've seen the fuel control solenoid cause a " cyclonic idle " where the rpm would go 200-300 rpm above and below the threshold. You can also see this happening monitoring the desired and actual rail psi. The actual will go above and below the setpoint by 1000-3000 psi. The rail pressure is controlled by the ecm cycling the fuel control solenoid, so no real pressure regulator in the system.