Truck (St. Louis MO) going to the dealer (I know it’s going to hurt), stop me if you

[eyyu]

Thanks for reading my long post and thanks in advance for any suggestions. Erwin

95 7.3 manual , with 96 computer. I tried everything I can and I’m really cold and tired. Made appointment to bring her in this Thursday. Their rate: $185 minimum to check it out, $125/Hr for trouble shooting, any parts they put in is mine! (of course the sales lady told me that their mechanic is very competent). I’m afraid that at the end of day, I’ll get lots of spare parts (ECU, IDM, IPR, etc.).

If you agree that she should go, anybody has a good Powerstroke mechanic shop in the area that you can recommend? I’m willing to cough up good amount of money ($1000 maybe) to pay for the labor, the parts that causing the problem. I’m just nervous about trusting someone in the dealership replacing major parts according to his “best judgment”.

It started to cut out occasionally (all RPMrange) a few months ago. I kind of ignored it since I can still drive it w/o being stalled (beauty of a clutch vs. auto). It got progressively worse to a point (now) that I do not want to take her out anymore. While it’s sitting, it can run just fine for hours (nice idle) or cut out every second. It will start right up no matter what. If I keep the rpm at around 2000, it will recover most of the time after the rpm drop.

AE scan shows HPOP pressure drops after rpm drop. Injector buzz test passes ever time and sounds right. Cylinder contribution test passes easily. No codes except the MAP.

Here is my capacities: AE scanner, good multimeter, good mechanical and electronic knowledge,
Here is what I have done:
1. Fresh Motorcraft oil a week ago. (engine runs good for two days after that. I thought that I fixed it). The oil in it was good generic oil (no anti foaming agent?). It did look foaming when I drained it. My big mistake using oil for modern diesel oil!
2. IPR rebuilt (o-rings, seal), everything look just right
3. runs the same with IP sensor unplugged
4. Have 4 new CPS on hand (3 gray, 1 blk), not a difference.
5. CPS wires checked out: continuity to ECU terminal good and no short to ground
6. When it’s running well, wiggle-checked all harnesses, connectors, plugs, no difference
7. Opened up the IDU, no water, no corrosion, all look fine inside. Tapped, twisted (lightly) the IDU board while running well, no differences. (I know it’s 110V, I was very careful running it with the IDU board w/o the alum box)
8. Did not take the ECU out (harder than I thought). Only checked the ECU connectors visually.
9. Fuel bowl out and cleaned, good fuel pressure while running (60 psi)

[atvrider93]

what oil is in it now?

[eyyu]

Originally Posted by atvrider93

what oil is in it now?

It's Motorcraft 15w40 super duty. I already discarded the bottles and box. But, here is what is on the invoice: XO*15w40*QSD. My gut feeling still tells me it's either CPS related or oil. Maybe I will do another oil change either with the same motorcraft or shell rottela T oil. I might go buy some more CPS, just to try, maybe one from international or just autozone (all 4 I got so far are from Ford). Erwin

[atvrider93]

the international CPS is good but after trying 4 I doubt its the CPS
put the rotella T in there with a motorcraft filter. make sure your fuel filter is good.
it sounds like the only thing you haven't checked is the ICP sensor.

[madpogue]

When it quits while you're underway, and (correct - nice thing about a 5-speed) the truck keeps turning the engine over as it rolls down the road, does the tach drop to zero, or does it continue to read an expected RPM? If it drops to zero, then that suggests an electronic problem -- CPS, PCM, etc. If it doesn't, that leans toward a fuel-related problem -- fuel pump, HPOP, injection pressure, IDM, etc (yeah, the IDM is "electronic", but it's on the "fuel" side of the equation). Not a conclusive / definitive finding, but at least it helps narrow down where to look.

[eyyu]

Originally Posted by madpogue

When it quits while you're underway, and (correct - nice thing about a 5-speed) the truck keeps turning the engine over as it rolls down the road, does the tach drop to zero, or does it continue to read an expected RPM? If it drops to zero, then that suggests an electronic problem -- CPS, PCM, etc. If it doesn't, that leans toward a fuel-related problem -- fuel pump, HPOP, injection pressure, IDM, etc (yeah, the IDM is "electronic", but it's on the "fuel" side of the equation). Not a conclusive / definitive finding, but at least it helps narrow down where to look.

1. Madpogue, the tach keeps reading the expected rpm.
2. ATVrider93, I might try Rotella T tomorrow. Also, I did forget to mention another small detail. That night when I was ready to do the oil change with my new case of Motorcraft oil, I realized that I forgot to get the filter from the dealer. I have to get the Fram filter from Autozone. I'll get the right filter tomorrow.
3. Tested the CPS circuit tonight. Here is the result.
-Continuity of all three wires tested good and signal wire (DG) no short to ground
-Key on engine off, BR/W wire: 5V; key on engine on, 5V; while dying, still 5V
-No scope to read CPS signal. Used multimeter. Key on engine off: DG wire 12V, key on engine on 6.4V, while dying, can’t tell if rpm drops first or signal.
---Conclusions: most likely CPS and wiring is indeed good

[eyyu]

Originally Posted by madpogue

When it quits while you're underway, and (correct - nice thing about a 5-speed) the truck keeps turning the engine over as it rolls down the road, does the tach drop to zero, or does it continue to read an expected RPM? If it drops to zero, then that suggests an electronic problem -- CPS, PCM, etc. If it doesn't, that leans toward a fuel-related problem -- fuel pump, HPOP, injection pressure, IDM, etc (yeah, the IDM is "electronic", but it's on the "fuel" side of the equation). Not a conclusive / definitive finding, but at least it helps narrow down where to look.

Madpogue, I agree with you that most likely it's fuel related. I just hooked up a pressure gauge to the shrader valve and was monitoring fuel pressure as it runs and dies. Here is the result: at idle, bunces between 50 and 70 psi. As it is dying, pressure stays above 50 and slowly drops after the engine was dead.
So fuel delivering system is fine. As to the ICP, I did run the engine with ICP unplugged, no difference.

So, what's left on the list? HPOP, injection pressure, IDM. I can test injection pressure (oil pressure) with my AE scanner. However, how can I tell which causes which, the engine (rpm) of the injection pressure? Erwin

[Patrick Feeley]

Here's a looooong shot and probably won't help, but try unplugging the Exhaust Back Pressure sensor. Sometimes they will short and if yours is intermittenty doing so, it could cause problems. It'll set a code for the EBPV, but you can always clear it. Cheers!

[eyyu]

Originally Posted by Patrick Feeley

Here's a looooong shot and probably won't help, but try unplugging the Exhaust Back Pressure sensor. Sometimes they will short and if yours is intermittenty doing so, it could cause problems. It'll set a code for the EBPV, but you can always clear it. Cheers!

thanks for the suggestion. I did run it with it unplugged, no difference. Erwin