Throttle stutter/truck jerks at highway speeds

[3rdgenmike]

Anyone have any idea on what could cause throttle stutter? My trucks an early 04. Around 1800-2100rpm the truck will jerk rapidly. My tuner says my pulsewidth is being erratic. Something is either causing the tps signal to drop in and out quickly, or there's interference. I've replaced the tps with a timbo unit, replaced both cam and crank sensors, and added the bd diesel ac noise isolator with no luck. When I set my meter to ac voltage and test the alternator, I get 0.006V, so I think that's fine. I haven't found any damaged wires and I have no idea on where to go next. 

[Tractorman]

Have you checked for any DTC's? 

 

Is fuel pressure where should be (lift pump pressure)?

 

What are the conditions of your battery cables (including the crossover cable) and battery connections - both positive and negative?

 

You may want to get the tuner completely out of the system to help diagnose. 

 

Please give some history about the truck - miles and years you have owned it and what you have done to it, etc.

 

- John

 

[3rdgenmike]

No DTC. fass shows 18psi. All new cables last year. Batteries are good, i tested them about a month ago at work. Even putting the stock file back into the truck, it'll still do it. 

 

I've had the truck for about 4-5 years now. Because I live in the salt belt, I did a cab swap about 3 years back. Dual stock cp3s, 209% injectors, rebuilt 6.7 with Brian Crower Rods, 625 studs, fire ringed fleece stage 3 head, 10 bar map sensor, 6.7 rail sensor, s467.6 over a psr 92. Trans has a solid input shaft with a 2600 stall converter, extreme intermediate shaft (the one where you gotta machine the overdrive planetaries), fat output shaft, muldooms fmvb, other basic billet parts. All the suspension has been replaced. Whole new ac system and steering system. Almost everything on the truck has been replaced within the last 4-5 years, except for any of the wiring in the truck. Dash shows a little over 248k miles.

[Tractorman]

Does your tuner read fuel pressure - commanded pressure and actual pressure?  If so, what is happening with these pressures when the stutter issue occurs?  Does the stutter between 1800 rpm and 2100 at any engine load, or a particular engine load?

 

There are people on this site that know more about the common rail fuel system than I do - maybe you will hear from them. 

 

Sounds like you know your truck pretty well.  Now that you mention operating the truck in the salt belt, I would definitely check wiring and wiring connections to sensors, ECM, frame grounds and body grounds, etc.

 

How about the possibility of bad fuel?  Might be worth a fuel filter change which would allow you to inspect the fuel passing through the filter, as well.

 

- John

[3rdgenmike]

24 minutes ago, Tractorman said:

Does your tuner read fuel pressure - commanded pressure and actual pressure?  If so, what is happening with these pressures when the stutter issue occurs?  Does the stutter between 1800 rpm and 2100 at any engine load, or a particular engine load?

 

There are people on this site that know more about the common rail fuel system than I do - maybe you will hear from them. 

 

Sounds like you know your truck pretty well.  Now that you mention operating the truck in the salt belt, I would definitely check wiring and wiring connections to sensors, ECM, frame grounds and body grounds, etc.

 

How about the possibility of bad fuel?  Might be worth a fuel filter change which would allow you to inspect the fuel passing through the filter, as well.

 

- John

Rail pressure is good. I did have an issue last year, truck would do almost the same thing and it was the rail pressure dropping for a split second. Sent a log off to my tuner and he fixed it. Seems to be under a certain load, unless I'm on the highway. Sometimes I can hear the rpm surging when I'm driving on the street, but most the time I can't. When I'm on the highway, it'll happen almost every time. 

 

I have changed my filters too, sadly didn't help. I've been fighting this issue for about 4 months now.