Hi guys, newbie here.

I have an 08 Super Duty, 6.4, Gearbox Z DPF-R, CAT & DPF removed, EGR plates installed. Occasionally, the truck will 'chug', spit out gray smoke. I let off the pedal, punch it and everything clears up. It does not happen every day. It will happen towing or not. There is no fluid loss. Air filter, oil filter, fuel filters have been replaced. There are no codes or CEL.

I have searched and cannot find a post with (all) of my symptoms. I suspect something with injection timing, but have not found a troubleshooting guide for that.

Thanks

 

I'd consider maybe a sticking injector. Run some diesel Kleen injector cleaner and see what happens.

Ensure it is for diesels.

 

Does it happen in rainy weather or during humid conditions? If so it could be from accumlated moisture in the CAC. A common problem in these trucks.

 

I am going on a 600 mile trip this weekend. I will pick up some injector cleaner ant try it out. Thanks

Also,
I had found the TSB about early 2008 trucks accumulating water from condensation in the bottom of the intercooler. I did check and mine is a late 2008. I also pulled the bottom boots off and checked the lower portion of the intercooler and it was dry. I also checked all the boots for cracks and they looked good.

Another odd factor is that it happens after a long, steady RPM. I can drive (interstate) 30 miles, come to a red light at an off-ramp and it will do it when I take off from a stop.
Smoke, Chugging I let off then punch it and it clears up after a few seconds.

That is what started my thinking it was something with timing. I suspect the Gearbox Z program modifies timing for fuel economy then resets for power, what the trigger points and sensors involved are I don't know....

 

Perhaps it is an EGR valve that may be sticking as well. Either way the injector cleaner will help.

 

Still sounds like the CAC issue to me.....

 

I have spent most of this morning reading posts on multiple sites about the CAC issue. One thing that is
confusing to me is that water in the bottom of the intercooler or present in the lower boot is common.
Mine is bone drive without a hint of condensation.

It looks like the CAC issue is still a mystery with some possible, but temporary fixes. Has anyone really
figured it out? It seem a lot of people have thrown a lot of money it it but no one (manufacturer) has
come out and said 'We have a fix and we guarantee it..'. Instead I see $ 1,700 intercooler kits and magic boots.

I'm an analyst by trade, and this still looks like a big question mark to me..... Has anyone
really pinpointed anything other than the anomaly being more prevalent in high humidity situations ?

 

I had my CAC replaced under the TSB. It helped a lot, but not a cure. Once I installed my Banks CAC, the problem totally disappeared. Certainly no "gaurentee", but it sure looks like the smart bet.

 

Likewise, the replacement helped a lot but under the right conditions I can still have the problem. for the price of the banks or spearco coolers I can live with what I have. If you are pulling the boot after an event that usually triggers the problem and the boot is dry I think you need to look elsewhere. But, if you pulled the boot on a dry day in your shop it may be worth further investigation. I say this only because it is such a well known problem. Do you note the stutter and smoke happening when damp outside. Cause I'll tell you the 30 mile run at cruise and then falling on it's face under power sure sounds like the CAC deal. You might try this, drive the 30 miles at cruise speed and just before you get ready to exit kick it in the azz and see if it fails. If the CAC has moisture accumulated it should.