So my buddy just picked up a late '99 CCLB Dually 7.3 from a coworker. It has 340,000 miles, but the truck is in such good shape and he paid so little for it that he could replace both the engine and transmission, and still have paid under book value for it.

We got it home, changed the oil and filter, and he put a bunch of hot-shot in at the suggestion of someone else, hooked FORScan up and did the full array of tests since it had a very obvious misfire. It came back with cylinders 1, 7 and 8 failing the CCT test, and #6 showed about 3% in the live-view. 1,7 and 8 were over 5%. I know from experience with other engines that when you have multiple dead cylinders, the contribution tests can get a little strange so we decided to pull the valve cover.

Buzz test indicated some of the injectors definitely had issues. 2 and 8 buzzed out excellent (they also had re-manufactured tags on them, PO told us he had a few injectors changed in 2011 or so), while 4 was a bit quieter and 6 barely made any noise at all. Unplugging #4 and #6 made no difference to the engine, while #2 and #8 drastically changed engine operation. We called a few local autoparts stores, and one actually had two injectors in stock, so we changed those out and took the truck for a drive.

The truck drove much, much better, however there was still a shake at idle. Now 1 & 7 and sometimes, but not always 3 fail the cylinder contribution test. 1 and 7 still buzz out very quiet as well, so obviously there are still some injector issues. However, we noticed after replacing the two bum injectors on the driver's side and taking it for a test drive - the truck actually had really good power despite having two, or possibly 3 dead cylinders. It was also shifting quite hard and firm. When looking at the scanner readout, the ICP would often exceed 3000 PSI, I believe I saw as high as 3100 PSI.

Is the hard shifting and high ICP evidence of a tune, or could the ICP be high from the bad injectors not utilizing all the available HPO? Is there any obvious way to see if this truck is tuned? Another question, is it normal for injectors to go bad just from sitting? The PO said the truck ran fine when he parked it, but I find it hard to believe that 4-5 injectors just completely packed it in sitting for a while. Although, granted with 340,000 miles, the original injectors were probably pretty tired anyways.

 

Have you pulled the PCM to see if it has an add on / chip?

 

How to the o-rings look on the injectors? A leaking o-ring cause cause ICP to skyrocket.

 

Sweet! Post up a pic of the little darlin! We likes peekchures.

Stuff like that is often recommended for 6.0, but for 7.3 just oil is fine. Synthetic oil if the injectors are tired.


Hard shift yes could be a tune, but not necessarily. Sudden lifting from WOT will spike the ICP to those levels. Continuous at 3100 psi is another matter. Monitor ICP duty cycle % and PSI.

Assuming it is normal operational spike, it's from all the injectors snapping closed at lift from WOT. The flow of HPO in the pipeline suddenly has nowhere to go. And not rapidly bleeding off thru bad o rings, so that's good.

As suggested pull or inspect the PCM for a chip stuffed in the end of it. A tune flashed onto the PCM from a Superchips programmer or similar is invisible. But a look at ICP % vs PSI can give a big clue.

No. But if PO was running synthetic and you put in dino iffy injectors will reveal their iffy-ness.

CCT often shows cylinder 3 and 8 as "bad" but that's normal depending on the CPS you are running. I'd trust the sound of a cold buzz test more to gauge injector condition.

 

There is so much going on in the truck that I don't think I have time to cover everything this morning.

1. Hot shot shook the snow globe up pretty good, there are no strongly-recommended additives for oil on a 7.3L. Since we don't suffer the "stiction" issue, this introduces a variable that's hard to suss out.
2. We are missing too many PIDs to have a full picture of what's going on in there.
3. Our friend aawlberninf350 is hinting at a possible "Stinky Spike", and we're back to needing more PIDs to isolate that.
4. A log of an array sensors during a WOT run is most helpful in troubleshooting this.
5. The UVCH link in my signature might yield some clues as well. Definitely worth a click and a read.

Here is a list of the PIDs that will help us figure this out - it will even tell us if you have a tune. Set FORScan to log these as you drive (including a WOT run), then you can share the log here:



Instead of Mass Fuel Desired, I'd use Torque Converter Slip.

 

It's been a while and my memory is not so good, are those max numbers the numbers that you recommend for graphing?

 

Yes, and I changed EBP to 55 max. These maximums make the graphing on AE work so much better than the default settings. If you don't set these, then many of the lines in the graph will be pretty flat and low - particularly FIPW.

 

Thanks for the info guys, we'll get a datalog as soon as possible.

 

So we ended up picking up 4 more injectors and we replaced the entire passenger side bank, since half of them failed the buzz test and the drivers side bank was basically brand new.

All of the old injector o-rings were no longer soft, the middle o-rings on 3 of the injectors were permanently stuck flat, and the bottom o-ring on one of the injectors was starting to tear and come apart. Another injector showed signs of combustion gasses getting past the copper washer. So needless to say, they were not very happy injectors. Not sure I can blame them considering the engine has 340,000 miles.

4 new injectors later, and the truck is now running absolutely fantastic! The 4 glow plugs on that side were also replaced with new Motorcraft plugs.

We let the engine warm up and took it for a drive. No more weird ICP spikes! Here's the IPR and ICP numbers, how are they looking?

Warm Idle: IPR 11.7%, ICP 490 PSI
WOT 2700 RPM: IPR 37%, ICP 2960 PSI

There are two issues remaining:
- We have an exhaust back pressure sensor circuit failure code. Is it likely to be the sensor, or the wiring? Does it impact engine operation in any way?

- Maximum boost seems low. It's making at most 11 PSI according to the Manifold Gauge Pressure PID. I'm thinking somewhere around 15-17 is what it should be making? Possible waste-gate or up-pipe problem?

 

Yep that sensor has impact. Not "go/no go" impact but still the PCM needs the info. Likely just needs cleaned, they foul with soot. To remove use two wrenches. Just one from above will bend the bracket. Hold bracket steady with 2nd wrench. I used a bent tip pick to clean mine. Be careful poking in there or you'll damage it. Tube can be cleaned with weed wacker cord or speedo wire held in a drill. They often crack too, and replacement is not expensive.


Yeah stock 15ish is normal. Likely worn collector up pipe gaskets. They always wear out, then allow exhaust pressure to escape and not pressurize the turbo. The killa fix is bellowed up pipes (either genuine IH $$$ or chinese Dorman $) or go cheap and replace the stock donuts with Felpro 8194. I did that and got 5 years out of them. Not a fun job but if you see soot streaks on the pipes below the collector there ya go. Lots of threads on that repair.