Rough idle , not overflow valve

[TMc]

Ok guys I've seen this question here before but never a resolution, so here it is again, I have a rough idle which is at its worst at about 1000 rpm and then of course slowly smoothes out as the rpm's climb. Overflow valve is new (solved powerloss problem) fuel pressure within spec at idle and at speed, fuel and air filter new, many tanks of different cetane diesel have been run through it to rule out bad diesel. Valves adjusted to spec. Truck has 90k on it and is all stock, performance mods ready to go but want this fixed beforehand. Rough idle started about 500 miles ago, no drop in performance associated. My last thought is dirty injectors... ... ..... has anybody had same problem and found resolution ?

 

[DieselB59]

I'd be more inclined to base the problem on an injection system problem rather than a transfer pump problem due to the pressures being correct. They were up to par with the new overflow, right? If so, I'd start by changing out the nozzles and working forward from there. A set of OEM nozzles can go much further than 90K, but it's always a good idea to get a reman set once you approach 100K. If that isn't the case it could be a problem stemming from inside the injection pump. Does the problem happen hot and cold? Do you see the engine shaking? These are the things that I'd be looking for when under the hood.

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Chris Timochko
AUTO WURKS DIESEL R&D TEAM
1997 5sp 4X4, Rhino Linings, Espar Heater, A. W. D. HX40 turbo, ATS 3pc Manifold, BD 4" Brake, Marine Compression, A. W. D. Custom Tuned Injection Pump, A. W. D. Intercooler, A. W. D. 370B Injection Nozzles, Delivery Valves, Governor & AFC Spring Kit, Psychotty Air, A. W. D. Water Injection, NOS Diesel Kit, A. W. D. 6" Chrome Exhaust System, BD No Smoke Valet Switch, McLeod Dual Disc Clutch, Mag-Hytec Rear Cover, Cummins Chrome Kit, Optima Red Tops, Hadley Bully Horns, Hurst Line Loc, Goodyear Wrangler AT/S 305/70/16s. 15. 50@97mph on Goodyear All-Terrain tires.
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Project U96 - 1996 3500 2WD racer. A. W. D. Marine Ultra Low Compression, A. W. D. Teflon-coated Pistons, A. W. D. High Lift Camshaft, Ported and Honed Cylinder Head, Intake and Exhaust manifold; A. W. D. HX40 Turbocharger, ATS 3pc Exhaust Manifold, A. W. D. Water Injection, A. W. D. Custom Fabricated Fuel System, Race Spec A. W. D. /BD P7100 Injection Pump, A. W. D. Custom High Flow Fuel Injection Nozzles, BD Auto transmission and Custom TC, Weld Draglites, Goodyear Eagle Drag Slicks, 5" Single Stack Through The Bed, Mag-Hytec on Rear and Transmission. 11. 54@115mph

 

[TMc]

DieselB59
Thanks for the reply, rough idle happens both hot and cold and yes I can see the engine shaking more than normal ( not extensively more ). I will be putting in a set of DD3's soon should I just see if that cures it assuming it is the injectors or can you give me anymore insight. Thanks in advance

 

[Strick-9]

TMc,

I too have a rough idle. Engine shakes more than normal. Happens both hot and cold. My engine is much louder than other cummins. ConleyJo came over a few weeks ago to get some help with a VB install. He heard my truck and said it sounded like it had a cam in it. #ad


I have about 10k miles on my Diamond B 370's. I installed a new overflow valve about 3k miles ago. I haven't check fuel pressure or timing. Those are next on my list.

I don't know what else it could be.

-Chris

'94 2500 4x4 w/ auto by DTT, diamond B 370's, high flow delivery valves, governor spring kit, modified AFC spring kit, extensive fuel mods, TCC unlocker, jardine 4" exhaust.

In the works: propane system designed for automatics, twins turbos