Current Problem: Truck stutters/flutters around 60mph/2000rpm's, only happens at highway speeds. No SES/No codes. Just started doing this last week.

Example: While driving down the highway tach gauge will flutter between 2000 and 1500three or four times in rapid succession. This can happen every couple of minutes or every couple of hours it just seems to have a mind of its own. There are no codes or SES light activity, and no smoke associated with this stutter/flutter. Someone please help.

When this problem started I thought the fuel filter was clogged changed it no difference. Moved on to the beginning of PMD problems changed the PMD and resistor and mounted on FSD cooler, still have the stutter/flutter problem. I now have a good deal of black smoke upon heavy acceleration I assume because of more fuel flow with the #9 resistor and still no turbo boost because of vacuum pump = more black smoke. I’ve done the lift pump test alls good, open the valve plenty of fuel flow and no stalling or sputtering. Also this occurs with cruise on or off so I’ve ruled out the pedal sensor.

History: 1st time diesel owner, truck has 193, xxx miles, I don’t think the vacuum pump has not worked since I bought the truck about three months ago, SES would occasionally come on, I forget the code but Walt at SS Diesel said the code usually indicated the wastegate actuator solenoid, I changed it no luck still threw the code. Traced the vacuum back to the pump it is definitely no good. Only mods are upgraded thermo housing and possibly water pump, pmd w/#9 resistor and FSD cooler mounted on the intake as suggested. Tomorrow I will be adding the flowmaster downtube and crossover, as well as a K&N type air intake.

Have the trans filter and fluid changed - not flushed - changed.

Engine problem would kick it outta cruise right real quick, like.

Post results, we can take it from there.

gmtdc,

thanks for the suggestion, first what is the difference, and second I had a "tranny service" done a couple months ago I know they changed the filter but I don't think they drained all the fluid and replaced with new I think it was just topped off.

if they changed the filter they should have changed the oil, as they had to drop it anyway to get the pan off. I cant see how they could reuse tranny oil, but i guess some garages will.

Flush gets the fluid back-flushed thru the trans cooler lines, reverse flowing thru the filter, supposedly cleaning it - but it don't.

Drop the pan, pitch the old fluid, clean the pan, remove the old filter, install a new one, new pan gasket, new DEXRON-III fluid.

Gives a good mechanic an idea of wear condition, what else may be needed.

The symptom you're describing is trans going in-out of TCC lockup or 4rth-3rd-4rth gear hunting.

Fluid starvation from blocked filter can cause that.

PCM modulates Line Pressure solenoid each minute to keep regulator valve stick-free - can cause that symptom also.

Won't set any DTC's.

Best to start with pan-off inspection, if the trans vintage is same mileage as odometer.

I would try cleaning the trany speed sensors too if its a 4x4 the back one is in the rear output of the transfer case. Unclip the wire, then use IIRC 13mm wrench, then turn the sensor about a 1/4 turn and pull out. Use something like brake-clean and a rag to clean it. I coat the o-ring with dielectric grease before reinstall it. I've never had to clean the front one just the rear one.

Carey

Let me understand this first.... You are cruising at 2000 rpms +/- at 60 mph, and the RPM's flutter DOWN to 1500 RPM's?

Am I wrong in thinking that this is more of an engine issue rather than a tranny issue? I thought tranny starvation would result in higher RPM's rather than dipping down. Or am I off my rocker?

I am with knkreb, sounds like a engine/ip/pmd then a tranny
does it smoke at all???
thought I do have one idea:
if the speed sensor was to go bad and make the ecm think it's going faster it could put the governor on or it the alt was going bad the ecm would that it's revin to high.. just a thought...

Later
Johnny

i have the same problem as xpoorpoetx. but i would sometimes stall drivin around town, and when it would stutter goin around 60, it would seem to drop alomst all the way down. changed the fuel filter and it seemed to work a lot better, but it still stalls everynow and then. i dont know what should be next. no ses codes.

I was interpreting it as trans would shift into 4rth, then TCC would lock, rpm would drop, than back out again, rpm would increase.

Anything else, cruise would unlock - but maybe it does, and he didn't say so.

No MIL SES would indicate fuel starvation, but where's DTC35?

Low Boost won't set DTC78 when blowing black smoke

He's gotta FSD\PMD, fuel filter and etc replacement

Ok, here's the scoop I spent the afternoon changing the vaccum pump, serpentine belt, tranny speed sensor, redoing the vacuum lines, and stripping out the factory airbox and snorkel. After all of that I still have the stutter/ flutter problem around 60mph/2000rpms but my black smoke is gone except at WOT. And now with the vacuum pump working and my new $25.00 Autozone/Home Depot intake setup I can definatley here the Turbo spooling (that's a great sound). Tommorow I'm opening up the exhaust with a Flowmaster downtube and crossover and 4in straight pipe.

Need to check fuel pressure. Install a "T" at the fuel inlet. Use a low pressure gauge and run it at speed. Suspect your running out of fuel. You did change the oil pressure switch, Right?

Ok, Here goes I've changed the rear speed sensor and the oil pressure sender, I've still got the problem. But here's the kicker I tow a trailer (a strange little thing a 16ft dock high cargo trailer it's a parachute and loaded it weighs in at 9000lbs) and when I'm pulling it my problem is gone not even a hiccup. Any ideas?