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Discussion Starter · #1 ·
Here's another clapped 7.3 update:

Driving through the mountains of Colorado, I made a few observations:
-Stomping the accelerator did not result in a puff of black smoke out the tailpipe like it normally does until I either downshift or hit boost
-It started taking longer to rev up
-I noticed a loss of initial torque(i.e. putting my foot down in 5th gear at 60mph didn't give me the usual power), until I hit boost.

For those who know, I pulled Monarch pass at ~60mph, light throttle in 5th gear. I do not have EGT gauges, but looking back on it, they were probably NOT pretty at all. I need to be more conservative pulling those kinds of passes.
On the way down, I completely lost power. Stomping the accelerator would make the truck slowly get up to 2000RPM, and hit a "fueling wall" where it would act as a rev limiter right there, billowing white smoke, with the occasional big puff of black smoke if I mashed the throttle a few times in quick succession. Pulled off and checked fluids, and they were all fine, just how they were before the trip. Limped it into town, and noticed it would not go past 2000 even free-revving in the parking lot, so I know it's not necessarily a boost problem.

I'm not even sure if thats a fueling problem either, as there's no load on the engine.

I've been trying to pull codes and do injector self-tests, which I was successful before. I can attach my data logs from previous instances where my FORSCAN would connect. However, I don't anymore. The port gets power but doesn't communicate, nor does my CEL illuminate. It illuminates only briefly for maybe a tenth of a second when you key-on, but I KNOW I have codes right now and it's not illuminated. Let me diverge into this issue for a bit:
Forums are saturated with posts saying the OBDII doesn't connect, because people use improper scan tools or it's just not getting power. I can confirm my cigar lighter fuse is intact, because my pin 4 and pin 16 show battery voltage when probed. Comparing resistance to my chassis ground on pin 4 also shows negligible resistance. I know pin 2 and 10 are communication ports, which I probed KOEO at .2V and 5V, respectively. This is exactly what they should be measuring at. The only better test I could do is to hook an oscilloscope up to pin 2, 10, with 4 as COM, and try and shoot for a decent sample rate to try and match binary waveforms to verify that the computer is, in fact, communicating. I then pulled the harness for the C202 bulkhead--which I deduced as the communications bus. Traced the circuits for these communication buses to pins 62 and 63 on C202(I forget the circuits--one of them was 915, I believe?) and can confirm I have continuity in the wiring. It's not a wiring issue that I have.

This leads me to my questions, for those who potentially get REALLY down and dirty with the circuits and electronics networking on these engines. Could a communications error on a sensor trigger a pull-up or pull-down effect on the bus, skewing the whole network? I would say most certainly not, because the whole reason the DLC exists is to trigger a check engine light when reference voltages are out of a certain parameter. I'd figure that a shorted sensor would trigger a CEL, not a network failure.

I did find some corrosion on the pin RIGHT below pin 62, which was for exhaust pressure sensor. This was peculiar, because the P.O. actually wired the EBPV to a switch in the cabin, which I use every once in a while as either a novelty or a very low-key engine brake. And, yes, I am aware of the potential issues of using the EBPV as an exhaust brake, and I can confirm I used it once on this drive, and the engine was only at 1750rpm or so, so no valvetrain damage would have even remotely occurred, unless some freak accident of worn valve stem seals occurred where my oil became aerated as it leaked into the valve cover.

Now, back to the main concern.

I wonder if all the corners and shifting grades up Monarch was enough to stir up some garbage in the bottom of my fuel tank? I was nearing a quarter tank on my back tank at the time and I wonder if I clogged the fuel filter or damaged the lift pump. I took out the fuel filter, and to no surprise, it looked perfect. It has less than 1000 miles on it.

Regardless, I cleaned up the pins and plugged it back in (battery disconnected, of course.) I re-connected the batteries and, just magically, the whole stuck-at-2000rpm issue was resolved. I am still misfiring when cold though, which I can probably trace to a bad injector(or failing IDM?). I drove the truck until it warmed up and then it started firing on all 8 again, and it had plenty of power, even though it still sounded like it had a slight miss. I could ride every gear out all the way to redline now. When I idle it, though, it occasionally skips and lopes and then corrects itself and idles smooth, and this process cycles. I had this issue earlier before that got traced to a poorly-connected injector wire, which I fixed and haven't had issues with anymore. The injectors all read 3.5 Ohms, which makes me then move onto my next train of thought:

Could it be a failing IDM? Or a bad PCM? The lack of communication at the DLC, despite having a working signal, could point towards that.
Should I try a different CPS? I don't know how much of a difference it would make, though.
Since I can't connect to the computer to do good diagnostic tests, I am thinking of this:
If my 2000rpm rev limit ever comes back, I am going to unplug ONE UVCH connector at a time, to kill half a bank, and then rev it to see if it still sputters and spews white smoke. Do this for each half-bank at a time. If it sputters at each connector, it is not one singular injector that is at fault, it is more likely a computer issue or a fueling issue.
Run a fuel pressure test, duh. I need to get my hands on a gauge.

I have one more thing to add: My friend was following behind me this whole trip, and said that his eyes would burn every time I let off. Sounds like, to me, that I have a sticky injector that's dumping fuel even after I let off, and it's going right out the tailpipe.

I'm thinking of getting a set of gauges, a hydra tune, and some full force 160/0 injectors to hold me until this school year is over, which I will then (try to) super duty-convert my engine, mostly, to a GTP38 and an intercooler on a superduty efuel system. In the mean time, though, can anyone see any potential issues if I do JUST the injectors and tune right now? (Assuming I do a fuel pressure test soon and it checks out okay)

Like would a bad PCM or something cause premature wear and/or damage on my new injectors?

I thank anyone who took their precious time to read this. I know it's a long one, and a very dense one, at that, but I just started my junior year of engineering school and car troubles is the last thing I have time to waste on. I'm too busy (and too broke, at that!) to pursue these issues for much longer so I'm trying to reach out and get as many answers and brains together as I can.

Much appreciated!

More info on the truck:
333k miles
new genuine ICP and CPS ( F4TZ-12K073-C)
IPR is not replaced, but as of july 1 when I last was able to connect to the DLC I was showing perfect injection pressures, so I know it's working.

· Registered
25 Posts
Oooo kayyy, although I was initially going to mention a possible bad Turbo or lift pump, but sInce you lost me at FORSCAN and CEL, I'm definitely not the one to venture a guess at your question. It would seem to me that you have way more knowledge of what's happening with that truck than possibly anyone else here. Sooo... Have a great day and I hope you find your answer... LOL
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