Rough idle while cold
 

This week my 2006 5.9L Ram 3500 has developed a rough idle while cold. Once the truck reaches operating temperature, the roughness goes away. The truck accelerates fine and seems to have all the power it's aways had... even cold.

The truck has no chip and is completely stock with 117k miles. The truck only smokes a little when first started (not much), during heavy acceleration and some while towing. At idle and light/normal acceleration I do not notice any smoke and I have never noticed a huge cloud of smoke behind the truck.

I have not changed the fuel filter in a few years (maybe 15k miles or so) and will do that this weekend as well as add a fuel additive to the tank... Howe's & Power Service seem to be recommended by folks on this site. I will also check the oil to see if it's above normal level or seems to have fuel in it. The check engine light is not on currently, but I can also check for codes.

The truck has no fuel gauges... and I only have basic mechanics tools. Is there anything else I can check or that might explain the rough idle while cold?

Thanks,
John.

May have an injector going south. A sign will be white smoke at startup cold.

Update...
 

After work I purchased a replacement fuel filter and a 16oz bottle of Power Service Diesel Kleen. After supper I checked the oil and all looked fine with the consistency and level where they should be.

I changed the fuel filter and didn't see anything abnormal. I had my son turn the ignition on while the filter was out and the bowl filled in a few seconds. I started the truck and the engine ran rough with a little white smoke from the tail pipe.

The tank was half full so I ran to the station to add the bottle of Power Service and top it off. After the truck reached operating temperature, the rough idle smoothed out.

I drove for about 10 miles... hard accelerate, slow, hard accelerate, repeat. During hard acceleration I noticed smoke in my rear view mirror in the headlights behind me, but I could not tell what color. Near the end of the trip I didn't notice any smoke under hard acceleration... interesting.

This morning I woke and started the truck... it ran much smoother and I didn't notice much (if any) smoke. So far, I'm pleased with the results.... only time will tell.

I'll post a follow up in a few days after a weekend of driving.

Thanks,
John.

I experienced a rough idle when I first bought my 05 with 23k miles on the clock. The dealer could not seem to get a handle on it, replaced two injectors and it still occasionally did it.

I tried Power Service Diesel Kleen and after only a few miles I no longer experienced a rough idle.....still running good 4 years later. I am a real believer in Power Service in the gray bottle!!! I continue to use it every fill up.

Well, after a few days the rough idle when cold continued. :(

After a while it began to run rough even when warm, but not always. A trip to the dealer revealed a bad #3 injector. The injector was replaced ($960), valves adjusted ($400), and an upper ball joint replaced ($300). My wallet is $1,700 lighter, but the truck runs MUCH smoother now.

The mechanic showed me the injector feed tube... it was pitted with rust. So, I may have other injectors going out. After some research... if I suspect the same problem again, I will replace all 6 injectors and feed tubes myself.

Oh well, all is good for now.

Thanks!
John.

I'm having similar problems with my truck as of two days ago. I got back from a thousand mile trip, and it was on empty. I dumped a 5 gal jug of diesel that I had carried as extra fuel "just in case" that I filled up just before the trip a week prior. Since then, it has idled poorly.

Basically, start it, and it idles VERY roughly and blows white smoke. Sometimes it stalls. Eventually it smooths out. Then it drives fine. Sometimes when I come to a stop and clutch in, the idle seesaws and it may be a little rough, other times it's fine. But the problem returns once I start it again.

I changed the fuel filter... it looked like it had some goop on it... little dots or something. No real change. I added five gallons of diesel and dumped in a few ounces of HUM OUT (all they had in stock). I guess I need to drive it a bit.

I sure hope I don't have injectors going. I just put $1600 worth of new tires on it. I don't need anything else failing right now.

Rob

If you found an injector tube with rust, I'm sorry to say you likely have huge fuel system problems.

Since the fuel system is a "common rail", if you have rust in one injector tube there is most likely rust everywhere including in the CP3 high pressure fuel pump.

I would recommend to drop the tank, & clean & flush it and the entire fuel system. Check and examine all the fuel lines, injector lines and tubes.

I would then recommend to add additional fuel filtration & water capture.

Then hope for the best, start saving for a Cp3 and more injectors.

Good luck..