silver_goat

I have noticed that my truck has seemed to develop a very uneven idle. It sounds like a gasser with a large cam. It does not do it all the time and mostly when cold or warm and idling for a few minutes. It also seems to have gotten louder lately and lopes more often now. I have 50k on my truck and it has good power and no loss of fuel mileage.

I checked my fuel and replaced the fuel filter but that did not seem to help. I also added some Power Service fuel conditioner and it helped to quite it down some.

Any idea on what's going on? Do I have a fuel system problem or maybe a Crankshaft Position Sensor problem that's effecting timing? I am thinking about taking it into the dealer but I do not want to pay the $100 dollars for them to scan it and find no codes, and tell me there's no problem.

J BODY

You're going to have to have it scanned to monitor the rail psi or to even cancel injectors. Hopefully you can find someone who knows what they are looking at. I had my butt kicked hard by three common rail trucks when they first came out so I got a good education on how they work. I've replaced a couple of CP pumps because the electronic fuel control actuator went bad. That caused a "wave" like idle as the fuel rail psi would vary from 4500psi to 7500psi. Good luck.

R.M.THOMPSON

Our trucks cylinders fire about once a secound at aprox. 750 rpms,a specific over or under fire will generally stand out as it allows the other five to blend into the background. An infrared thermometer may help a little if it a specific cylinder or injector,but just look for temp. differance an not actual temp.J-BODY has a very important point abuot consistant pressures and not all injectors can stand the variation ! You need to know if it is an isolated injector or a moving target before proceding.

dezeldog

Goat, my truck does the same thing. Took it tho the dealer yesterday and they scaned it and said that everything was ok. I've even noticed the "lope" at highway speeds ie 70---80 mph. The tech said that all the pressures were right where they should be. I'll wait and see if it gets any better or worse.

Jim

silver_goat

Thanks for the info. So if I understand this correctly it could be a pressure problem on the fuel rail. The CP3 provides the pressure to the rail and there is a fuel regulator of some sort to keep the fuel pressure constant to the injectors.

That would make sense on why the engine idle goes up and down based on the rail pressure.

So in need to know if the CP3 is providing the correct pressure to the fuel fail and if the pressure regulator on rail is keeping it constant at different rpm levels. Would a bad or leaking injector effect the rail pressure enough to cause this? I would think if an injector was leaking or bad there would be signs of it.( fuel in oil, heay black somke at low boost pressure)