A new Gremlin showed up today.

[BamaSixGun]

Today while idling, my truck would rev on it's own about 50 to 100 RPM's above the normal idling
and would do that up and down, up and down.

It hasn't done it everytime, but enough for me to know that it has never
done it before. Once even while in Drive with my foot on the brake.

Any ideas?

 

[ckamp52]

it wants to be turned loose haha i dunno do these trucks have cps's ?

 

[BamaSixGun]

How about the ICP (Injector Control Pressure sensor)?

 

[ckamp52]

i could definitely see that as a way it would "pulse" i almost said that it seems "plausible" ive been watching way to much mythbusters

 

[powerboatr]

50 to 100 is pretty much close to a normal event
remember the brains and all its sensors may not be all in sync., humidity, air temps, ficm, etc
with all that is going on in a 6.0 to keep it running 50-100 is not a worry thing...
unless starts jumping up and down real fast,
my 350 used to do the same thing when it sat idling for a few minutes.

my 8.3 isc does it
it will idle at 750 up to 800 to 830 down to 750 back up to 800 while in neutral

 

[Todd Tumbleston]

unhook the batteries and reboot her!

 

[RoyBoy]

Check to see if your engine oil is at all overfull. I run mine halfway in the "OK" area on the stick.

 

[snicklas]

Check to see if your engine oil is at all overfull. I run mine halfway in the "OK" area on the stick.

I have seen more that one member post that suggestion. I change out 15 qts every time and it runs at "FULL"... have you seen somewhere to run it a quart low? I know not to fill the DEGAS bottle to even the min level... but have not seen anything "Official" on the oil level....

 

[BamaSixGun]

Check to see if your engine oil is at all overfull. I run mine halfway in the "OK" area on the stick.

Oil levels are A OK.

Again, this is the first time this "pulse" has ever occured, so

 

[snicklas]

I have had it a couple of times. The first time was right after I got the truck, I was sitting at McD's Drive up and it pulsed several times while sitting in line. I had newer oil and and unknown time on the fuel filters. Did my first service and changed oil and fuel filters and it didn't do it again untill...

Last weekend, we were on a trip back from Kentucky and I pulled off the interstate, I was pulling an empty 6x12 Box Trailer and had been on the Interstate for a couple of hours, and the truck had been running since we left, maybe 3 hours total, and once again in a McD drive up, it was pulsing, just enought to see the tach needle move and you could hear it more. I am due for an oil and fuel filter change.... 5k on oil, 10 k on fuel....

May be a sign of a needed fuel filter change......