Miss at high rail pressure, 6.7

[mr.mindless]

Hey everybody, it's been a while! And I'm back with a problem...

 

07.5 6.7, 370k. Two owners ago supposedly replaced the whole top end of the motor at about 320k chasing what turned out to be a bad EGR cooler. The truck had been stock until then. It got a new head, new turbo, new injectors, and an H&S with SmartyJr. I run either econ or tow with default values.

 

I've had the truck for a year and about 15k miles. It has been flawless with the exception of what sounds like chipped teeth in 5th gear that I'm ignoring... The last few days I've noticed what feels like a miss under high load. I have an Insight CTS, and watching what it's telling me I see no oddities in rail pressure, EGT, load, anything. It happens above about 20k rail pressure. If I back off it smooths out, if I upshift and lug it the rail pressure drops at a lower RPM and it smooths out.

 

I have no smoke, no gained oil, no rough idle, no miss at low load. It's pretty subtle, along the lines of an exhaust leak. I had no end of issues with injection lines on my P7100 24v though and it's attuned me to what a dead hole feels like, and this doesn't feel right.

 

I did get a tank of watery fuel over the winter once. I'd be less concerned if it wasn't for that.

 

Planning to pull all 6 sticks and bring them to D&W Diesel for testing. Crappy thing is I have a race this weekend and would like to tow down Friday morning, and they're backed up a couple days on testing!

[mr.mindless]

Also -

I've seen varying reports on whether the ECU needs to be programmed with the injector codes. Any knowledge to share?

Opinions on the smartness of replacing only one/some injectors and not doing it as a set? I've been under the impression that as long as they "match" CR can be replaced piecemeal, not like the older injection systems.

[dorkweed]

The only thing I can think of would be that you're "draining the rail"......................are you maintaining 20,000+psi when this starts, or are you getting out of the throttle then???

[mr.mindless]

Absolutely not. Rail pressure is rock steady. No notable fluctuations in boost or pyro, low of high pressure fuel.

Injectors are out and in dropping them at D&W Diesel first thing tmw.

Snark: I'd post pics if I had tapatalk

[AH64ID]

Do you have and H&S or a Smarty Jr?

Have you tried running different tunes?

The injector codes are calibration codes, so I would say then need to be programmed.

[dorkweed]

Please tell us what you find out!!

[mr.mindless]

Finally finished testing this morning. No leakers but #1 and #6 are out of spec with high return meaning they're shorting me on fuel. #5 has a broken alignment roll pin (that's the one whose hold down felt loose, god I hope that didn't go down the hole) and along with #2 it's at the return limit spec.

So I'm gonna put 6 reman injectors in it. Given age and history I don't know if these could potentially be aftermarket tips or anything like that and I'm not going to spend this kind of money to gamble on four fresh remans matching flow of two in spec unknowns.

Shitty but it is what it is. At least I don't have to worry about having melted anything with leaky tips, and testing was only $23/ea.

[MnTom]

I'm glad you figured out what seems to be the problem. That is not a bad price for getting them checked, but now you need new ones..... that can get real pricey. Maybe I should keep my poor old 12 valve!

[AH64ID]

I would think twice about remans, haven't heard about too many of them actually working for too long, or at all.