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Discussion Starter #1
Hello all. First time posting to the site. I have a 1997 F250HD 7.3 manual ZF5 short bed crew cab with 207,000 miles. I have owned the truck for 4 years and roughly 40K miles. Until recently the only engine mods have been the AFE cold air intake and MBRP 4" turbo back exhaust with cat delete and 3" downpipe. I change the oil every 5K miles and always run Rotella T4 15W-40 and Wix XP oil filter. I also change the fuel filter every 10K miles with Wix filter. Overall I think the truck has run well considering it is 22 year old. Cold starting seemed to be the only nuisance. It is my daily driver and is parked in the garage. When starting in the morning if I drove it the day before it would fire up pretty quickly, but if left for a few days starting up would take quite a bit of cranking and lots of black to white smoke. Once running idle seemed to be decent but not great. All of this i chalked up to the quirks of an old diesel truck.

A few weeks ago I decided to see if I could improve the cold start. I inspected the wiring harness connections and found the pigtail connections on the rear of the motor were fried. Looked to be the glow plug connections for #5, #7 and #8 were all bad. Instead of just replacing the connectors I decided to jump in and replace the injectors, valve cover gaskets, glow plugs and pigtails. I ordered 8 Full Force Stage 1 180cc injectors, 2 new Alliant valve cover gaskets/harness, 4 new Alliant pigtail connectors, and 8 new Motorcraft glow plugs. To run the upgraded injectors I also purchased the PHP Hydra chip (no chip had been run on the truck before). Last weekend I installed everything without issue. Truck fired up super fast and seemed to be great even after sitting for a few days.

Then I did some test drives and noticed some issues. At low speeds all seems well, First to second shift good, second to third shift good, but above that the truck shifted really funny. When accelerating in third gear up above 1500 rpm and then engage the clutch to shift the rpm's would drop drastically down below 400. If I tried to engage the next gear as normal the truck would "clunk" as if it was hesitating. This was true in the next shift forth to fifth as well. Also if I waited to engage the next gear the rpm's would drop below 400 and bounce back up to 650. This would happen about three times until the engine leveled off at normal idle rpm of 650. If i keep the shift points below 1500 rpm it doesn't seem to be as bad, but if I step on it and get above 1500 - 3000 rpm it is really bad. Additionally if i really step on it in the lower gears, say 3000 rpm shift from second to third there is no issue and shifts perfectly.

So here is what I have done so far to fix the issue.
- replaced EBPS (both the sensor and the tube. I made sure to clean out the bracket at the sensor and the connection to the manifold as well.
- checked ICP sensor and found some oil in the connection. Replaced with new sensor.
- opened valve covers again and re-torqued the injector hold downs (all good)
- visually inspected wiring and connections (all good)
- OHM tested the injector wiring and harness at the injectors all the way back to the IDM. (all ohm tests were good and all continuity checks were good)
- buzz tested injectors using OBDlink MX+ wifi dongle to iPhone app FORScan.

Here is where I really get confused. the buzz test runs and all the injectors buzz appropriately and sound the same. I did this with the motor both warmed up and the next morning totally cold. Each time the test comes back with failures to all injectors. Here are the codes...

P1271 to P1278, P1293, P1294, P1298 all failed.

I also removed the Hydra chip to see if that made a difference. The buzz test results are the same but the truck did seem to run better, but with less power of course. The shift issues also seemed to clear up as I did not get the rpm flutter between shifts.

The only other thing I can think of is a failing IDM. Before I keep throwing money at the issue I was hoping there were some more diagnostics I could do. Any help would be greatly appreciated.
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