bentwings

I have 321k on my truck. Very easy miles mostly highway and town and country.

A week ago the motor started a rolling idle rather than the smooth gentle diesel knock. When you drive 100 miles a day you get to know every sound the truck makes and when something changes.

It's not a big lope or really a misfire, the idle just rolls about 25 rpm according to the tach. It's about the same rpm change when you come to a stop. Manual trans.

There are no codes, nothing is amiss on the Gages. Gas mileage is still very good at 20/21, does not burn oil, no smoke. The truck runs just fine except for this idle change.

I opened the drain on the fuel filter and no water came out. It has a filter change about 6k miles along with lift pump. It failed right I the driveway so I didn't drive it at all. I have a gage. Currently it runs 13 idle and 11 cruising.

It could probably use a valve adjust and blow the trash off the radiator.

It has a new crank position sensor this spring, lift pump and fuel filter. We have pretty good fuel here in Minn. I did clean the battery grounds a month ago.

Any ideas??

SIXSLUG

Apps?

KATOOM

You could try resetting the APPS and see if that changes anything.

bentwings

Thanks for the replys.

I did some searching for info on the apps. Timbro looks like the way to go.

I have had some surging with the cruise control. Also I see the speedo drop occasionally.

What about injectors? Do they gradually go bad? One of the local guys suggested installing RV injectors.

KATOOM

Generally cruise control surging is related to the addition of a timing/fueling boxe. The more aggressive the box, the more pronounced the cruise control surging. If you have the vacuum controlled CC then you could check out the vacuum line under the drivers side battery which runs to the CC vacuum pod. Sometimes battery corrosion corrodes that line.

If you're having tachometer problems then maybe your CPS is acting up.

And no, injectors dont really "go bad" like that. But the RV injectors that person is telling you about are the RV275's which are new Bosch products and a nice mild addition to power and fuel mileage. But changing injectors to see if that helps your idle would be last on the list.

bentwings

Thanks,
Now I'm getting something I want to hear.....low cost and repair I can do without being in the shop. (Space and availability are a premium)

I assume you mean crank position sensor...CPS. I have replaced this so many times I have a "kit" ...tools and sensor in a plastic box. I get about a year or 20-25k on one. Even the Cummins one doesn't last. They are never physically damaged or "hit" but if the motor doesn't start in a couple revolutions it's CPS time. The code reader will pick it up every time and no CEL. Fortunately in my old age I have lost some body mass and I can just squeeze under the truck to do the job. -20 deg weather being the exception...then it's AAA to the truck shop. Haha.

I had not thought of the vac system. I'll have to check this out at work in the morning.

I do have a Smarty set to #1 which is timing. I've had this for over 200k and it does get better mpg and up until this started no problem. I'll also uninstall it before it fill up tomorrow. That way I can test it for the problem as well as mpg as I keep track of mpg closely.

I appreciate the help.
Thanks