Slight miss - possible cause?

[Tom W]

Just recently developed a slight miss, noticabled at low RPM, under power, cruising OK and not noticable at higher RPM under WOT. Not a solid miss, just not the usual smooth power. I first thought maybe bad fuel or water, I'm now halfway thru the 2nd tank and still does it. I use Standyne additive. Fuel pressure is good, 13lbs before and after filter. I disconnected the Banks ottomind, less power but still noticable. Anyone have any ideas? I plan to install new injectors soon but would like to find out what the problem is before I do that. I'm worried about the injector pump, what's the symptoms when they go out?
Thanks for the help. Tom W


------------------
Tom W in Austin Tx 98 24v 2500 Quadcab, auto, 3. 54, lsd, Rhino, white/driftwood, Banks Stinger Plus, Manix grill, nerf bars , DTT's TC, valvebody, cooler, Mag-hytec trans & diff, Pac brake.

 

[ynot]

Tom, mine started doing the same thing at 20,000mls. By 30,000, it was so bad I couldn't drive it anymore with a trailer. After 8 days at the dealer replacing t-pump, TPS, ECM, etc, and a call to Blue Chip (HOTVP44 first discovered this problem a couple years ago), they put a new injection pump on it and pretty much fixed it (about 90%). The timing solenoid catches PWM shadow pulses from all kinds of stuff on the motor and makes it jump all over hell. The new pumps with ceramic rollers also have an isolator for both of the solenoids, shielding them as best they can from the rest of the electrical system. Anything you do to enhance fuel delivery (i. e. fueling boxes, injectors, etc. ) will make it worse. Good luck... T

 

[Craig DeYoung]

Tom,
I have noticed a miss also the past few weeks. Mine is at hot idle only. I replaced my lift pump, new one passes volume flow test and is 11 psi at high-pressure pump inlet cruising. Next I'm checking vacuum in the line between tank and lift pump. Interesting note: I loosened my fuel cap to see if I was generating a vacuum in the tank (see issue 31 p. 86). Didn't fix idle miss, but my fuel gauge is behaving for the first time in three years. Wondering if I have internal wear on an injector or a leaking injector. I'll probably bring it in soon if I can't figure it out. 75K, still under warranty...

------------------
1998. 5 BE7L33 4x4, NV4500HD, 3. 54s, 255/85-16 Mud Rovers, Cummins uprate kit, VDO gauges

 

[DavidTD]

Craig and others, My 98 had the same miss when hot. Only at idle. After a VP44, lift pump, APPS, they changed injectors and the problem went away. Good Luck.


------------------
David
1998 3500 QC 4x4 5 speed 4:10, 235-85-16, VA CPC via JRE, PS Boost Module, K&N air filter. Emerald Green w/tan leather. B&W turnover ball.
1/4 mile 18. 2 @ 74. 75mph
1999 Exiss 3 horse slant, 4ft midtack, 6ft shortwall dressing.
70k miles as of 6/21/00

 

[ynot]

Well, the miss is back again. Not a "hot injector miss" (tip seating prob) like some of ya'll have, more like an electronic surge. Seems to be most prevalent from 1500 to 2250 now, and about the same axact thing Tom W. "spoke" of. I've seen a couple people have the same prob, but never caught what the fix was, if there was one. Blue Chip says it can't be fixed (tho they build a fueling box that they say will compensate for it), but I have the same set-up as a bunch of ya'll (barring the stereo system, but I unhooked it all for a test run, and it didn't change), and very few seem to have this prob. It started the same time I switched turbine housings, so I'm changing to a 16nwg today. I know it's a reach, but I'm running out of ideas, and 54 psi boost is a little much for the cooler anyway. The only thing left after that is different injectors and something to radically modify the timing curve, as to raise the PWM of the timing solenoid to put in a different range of whatever MIGHT be interfering in the system. Anyone else have a thought or heard anything that might help? It's a real ***** to drive on the solid ice layer we've had up here for half of the winter. Also curious if anyone has stacked a PE with an EZ, VA and whatever else I've seen on here you can combine with appreciable gains over separate components. I understand the "Law of Diminishing Returns", but more fuel is more fuel #ad
Thanks... T

------------------
Tony L. Welch
Welch Performance Diesel
2001 2500 QC/SB, ETH/DEE, trailer tow, camper special, Hunter green, loaded except leather, Pioneer 9200 dot matrix with Rockford Lightning 4. 600i amp/ Rockford Punch 250a2 sub amp, Alpine BBE 11ch EQ, Boston Pro 6x9's front, Pioneer IMPP 6x9's rear, Kicker Solobaric sub, Lowrance GPS, Galaxy 73 side band, Brite Box, "Turbo Saver" shutdown, 2whl low kit, stainless rocker panels & fender gaurds, 12. 5x33's on Pro-69 directionals, diamond plate bed and gate liner w/rubber mats, 14cm2 ported, Pacbrake (ported), compressor housing and elbow ported, intake crossover ported, K&N in factory airbox sleeved into cowl, 4" Dynomax, triple gauges (ISSPRO/ console), PE maxed, DDIII's. Clutch #7 on the way...

 

[Vaughn MacKenzie]

Craig & Ynott, just wondering about an update on your rough idle problems.

Mine has a miss at idle as well, while it does it very slightly when cold, it is much worse when warm. Several other Dodge/Cummins I've ridden in lately idle so smooth compared to mine it is sickening #ad
When revving it in neutral the RPMs surge and the combustion noise changes pitch and sound quality constantly. Going down the road I can feel it at light throttle and it is quite annoying. It is getting worse and worse, it feels uneven at all RPMs and engine loads now. I may have two issues going on at the same time. . . injector or tube problem, and some sort of electrical glitch (faulty sensor, connection problem, Injection pump PWM noise, etc. ).

I am going to start by removing and cleaning the injection tubes, maybe remove the injectors and have my neighbor clean and test popoff/bleed-down pressures since it won't cost that much (he's a diesel inj. mechanic). It is likely some dirt or debris got into the system since I removed the fuel lines several times doing R&D on the Aeroquip hoses. I am running RV injectors and it could be they are off quite a bit since they do not come balanced or anything. I hope to start some diagnostics this week or weekend and will post what I find out. Other than this annoying problem the truck has great power and I'm getting good mileage, 22mpg on the last tank, mostly hiway, driving it pretty hard and passing a lot on 2-laner.

Vaughn

------------------
'01 2500 QC Shortbed 2wd, 6-speed, 3. 54LSD, Cab & Fog lamps, Camper & Tow Pkg.
BOMBed: RV injectors, PS Boost module, Amsoil air filter, straightpiped exh. , Aeroquip 3/8" fuel line w/tank mounted lift pump, AutoMeter Sport Comp gauges, Line-X'd, Amber turn signal conversion.
Mildly BOMBed Performance: 0-60 @ 10. 0 sec. ,
40-60 @ 5. 5 sec. ,
0-100 @ 24 sec.