a friend of mine had a 05 ram 2500 ctd. 4x4. auto trans. 5 inch straight piped exhaust. and a tuner. yesterday it was 25 degrees outside and he went to start it and at first it idled normal, but after about 5 min. the idle got real loopy. like it sounded like it had a massive cam in it. the truck was like just chugging. he says its suppose to do that and i have heard other truck do this before.

my question is simply, what causes the truck to "chug" like this at idle?

thanks

 

i presume the chug you are talking about is the 3 cylinder idle the engine computer will first ramp up engine rpm to build engine heat and if it thinks more heat is necessary it will run on 3 cyl to increase the time of warmup

 

I have never heard the 3 cyl idle in person. I've had an '00, '01, '06 and '08 cummins trucks and idled them @ temps down near 0F, I never had any of them go into the 3cyl idle. I sure wouldn't think they would do it @ 25F. I can't remember the specs for what triggers the 3cyl idle, but 25F seems pretty warm.

Jeff.

 

I am having the same problem. At first I thought it may be the inj pump going out. After replacing the pump. I still have the same problem but only after the truck is fully warmed up
My truck is a 2001 with 220,000 miles on it