When letting the truck warm up in the morning, at 1100 rpm with the EB on, I notice a very slight miss/vibration. It does not do it if I kick off the EB and it seems to go away if I increase the speed with the engine brake on. When the engine is warm and idling there is absolutely no vibration that can be felt. With the hood open and my hand on the cylinder head, there does not seem to be any vibration except for normal engine reciprocating . I even tried raising the rpm to 1100 with the tranny in drive and no noticeable vibration.

I have the Cali deletes done, Smarty JR is V23 and set on the 40hp fuel economy tune. I reloaded to stock and it still happens. When I mean a very slight, I mean VERY slight. I am running some injector/fuel system condition through it as we speak, but was wondering other 6.7 owners have noticed this? Truck has about 75,000 miles on it, the oil is nice and clean, no diesel smell to it at all, there are no codes, antifreeze seems fine, its getting GREAT fuel economy, lots of power, no smoke at startup except for a slight black puff, no smoke when I put the hammer down (in controlled conditions of course). Am I paranoid? (well I already know that question)

 

6 cylinder engines don't really like 1100 rpm much. I know when I was driving over the road, I had a CAT tech tell me that whenever I had high idle engaged to ALWAYS go at least 50 rpm past 1100 (or go higher) as the harmonics at that rpm and the injector (electrical side) don't like it.

basically like our trucks with the dual mass flywheel (manual trans trucks) when the flywheel starts to come apart. the harmonics of it will set a check engine light and set crank sensor codes and cause the injector to seem to have a dead hole. i have seen techs chase that code for hours. then come up to them and tell them to check flywheel and low and behold there it is.

 

The miss I notice comes with either the cycling of the A/C compressor or the alternator for the grid heaters. If both engage at the same time I tend to see its more aggressive. The programming of the ECM is too sensitive to me and tries to maintain that set point no matter what. My old 97 just drops about 200 rpm and bounces back after the AC cycles out.

 

Ok, just a little more info on this, it only does it when warming up and is not constant (its not related to the grid heaters or A/C, I know when those kick in), when the engine is hot, kicked up to 1100 rpm (using the cruise fast idle), there is no miss/vibration at all. I think I'm going bonkers with this OCD that I appear to have. I should just drive the truck and enjoy it. We are going to Revelstoke with the TT the end of July so maybe a good pull in the mountains will put this to rest once and for all.

 

Even when its hot I see the same when the AC cycles. May or may not be the same thing. But I wouldn't worry about it.

 

Ok, a little more testing this am, it was too warm for the EB to warm up the motor, but at 1100 there is a definite miss/vibration that seems to follow the rpm (but do not hear any sort of miss when listening to the exhaust note). I increase it to 1200-1300 and its still there, but it seems to go away when warm. I just don't understand it. Can anyone else take a look at their motor first thing in the morning warming up on high idle and let me know if they see the same thing?

 

So is this an intermittent miss or a constant thing?

 

it seems to be constant, but if you engage and disengage the EB is seems to go away for a bit. But only when cold, once warmed up, there is nothing.

 

did you just notice this happening since you upgraded to v23? what you describe sounds like the same thing my truck does. i don't deem it an issue though.

*never mind just notices you said it does same thing with stock program*

 

No, it did it on V21 also. Nothing else seems to be an issue, and the truck appears to be happy. Looking forward to trying the 6.7 and TT in the mountains this summer with the engine brake.