RPM Fluctuation at Idle

[snicklas]

I have a 2003 Excursion and I am hearing some idle fluctuations. It only seems to happen while in gear (Torkshift auto) and has been at idle for a while. I.E. in line at a drive-up or positioning a trailer. It is only a momentary increase, it doesn't register on the tach, but I can hear it increase. It will idle fine in park or neutral. It doesn't do it all the time. It starts fine and seem to have a smooth idle otherwise. Any suggestions?

 

[Mike]

Fan clutch?

 

[snicklas]

I am actually hearing an increase in RPM. Or could it be a compensation for the fan?

 

[tbirdfiend281]

if your rpm's dont actually increase then it is a fuel trim being changed to compensate for an added or decreased load

your fan clutch locking up will not change the pitch in your motor sound

EGR will do it
Baised ICP sensor will do it
Fuel Quality will do it

how many miles are on your truck?
is there any large visable oil leaks?

 

[snicklas]

The truck has just a hair under 67K on it. I am the second owner and have had it for only about a month. There is a small amount of oil on the pan, but not enough to drip on the floor. To me it looks like a messy oil change, but....... The oil was changed just before I bought it, and it really doesn't look "fresh". I have not yet changed the fuel filters, and the batteries were shot when I test drove it and the dealer replaced them with a set of NAPA batteries. I have less than 3k on it myself, could it still be "learning"? At other times is seems to have a slightly rough idle. I have also heard, what sounds like the "THUD" described in another thread. I only seem to hear that in 3rd gear in "normal" mode, not T/H.

 

[tbirdfiend281]

ok well the small oil disprove my theory. when these suckers leak they LEAK, so the minor amount of oil is very acceptable.

make sure you do the fuel filters 10-15k on the money, not any more then 15k on a filter change, this is one of the most critical things to keep up on

is there any smoke coming from the exhaust of this truck at all?

describe this thud, is it on the downshift, upshift, cruising, accel, or deccel in the gear

 

[snicklas]

It is probably the filters. The last time that I have any proof the filters were changed is a piece of tape under the hood with "Fuel done at 32K" written on it. So if that is the last time they were changed, it have about 33K on the filters. I will pick both filters up this weekend and change them out.

I do get smoke from the truck on a hard acceleration, as the turbo is spooling, It is just a light haze though, I can see it better at night in the headlights of the car behind me. There is a light amount of sooting on the bottom of the back bumper, not bad, just looks like it is a little dirty.

It is a chunk kind of sound. It sounds like there is almost a pause, like the drive line is relaxed for a second. It is similar to the sound when you shift from reverse to drive, or if you are parked on an incline and take it out of park. It is not that "hard" of a sound though. It is only something I can hear, there is no "feel" associated with it. The thud is only on a medium acceleration, shifting from 3rd to 4th. I don't notice if I am easy on the throttle, or if I am getting after it. But under a fairly normal, away from the stop light and get up to speed kinda acceleration.

I hope that I have not rambled on to much. But I am computer admin and I like all the info I can get. Ask Trav, (argve) I can get detailed when giving info. He and I are good friends, I am just a littler easier on the equipment.

Thanks,

 

[powerboatr]

idle fluctuation at idle in gear or in park/nuetral is normal even by a few hundred rpms
the engine and al lits senosrs constly try to get it to run on the east amount of fuel and then compensate whne the a/c kicks on and off and the electri loads change

if your sitting in say a drive thru waiting on a mac nugget
the engine wil col ff some which changes idle parameters
the tranny will be heating up some from jsut sitting and throwing all that fluid at teh torque convertor
if yu have the a/c on normal it will cycle on and off more than if its on max which again will cause some good variations

you need to worry if it drops to low to run or ramps up to over 850 in drive for a prolonged period (over 20 secnds)

you said filters need changing and oil is not as clean as it should be
yep dirty oil or the remenats from not often oil changes will cause some fluctuations

 

[tbirdfiend281]

i think with 33k on the filters you would be having cold start missing/power problems/bucking/ among other things going on, do them anyway, they where probably done around 40 or 50k. then again you never know maybe 32k was the last time.

you need to be 100% up with everything before i can point you in the direction of potentials failures unrelated to PM.

what color smoke?

 

[snicklas]

tbird....

I have changed both fuel filters. The truck seems to run better and starts a little quicker. I have been running the Power Service additive to lube the pump and injectors. I am at about 3k on the engine oil. Still need to get it in for a tranny service and need to change the diffs and x-fer case. The smoke was a black color, but no matter what I did today, after the filter change, could I get the truck to smoke.

Scott

 

[tbirdfiend281]

well thats good, i think you have helped it then

make sure to do the auxilary transmission filter on the passenger side, ill try and snap a picture of one at work tomrow to show you what it looks like

the ford power booster?

cetane boosters gain mpg and help performance of the truck overall also...

i think the funky idle was probably the filters geting a little old, i would guess they where probably done around the mid 40k milege range and where probably geting a bit clogged

 

[snicklas]

I have seen the filter behind the radiator. Is there a screen in the Transmission Pan that needs replaced also?

The additive that I have been using is:
http://www.powerservice.com/dk/ - In the sumer
http://www.powerservice.com/dfs/ - In the winter

I have noticed an improvement in the truck since I changed the filters. I have seen it smoke, but only at night, and it is just a haze.

Thanks for the help.

Scott

 

[TEXCRAWLER]

I had servere RPM fluxuation that caused a turbo to go bad. I always keep my fuel filters changed. The rpm's would flux in drive, park, and then would shut the engine below 500 rpm's and then just shut off. Just put a brand new EGR valve in and seems to be running alot better.