Help! Hard miss under load - Ford Powerstroke Diesel Forum
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Old 08-05-2012, 11:15 AM
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Help! Hard miss under load

Hello all,

I have been lurking and using all the helpful threads here since I got my truck this spring, but I have had one major unresolved issue and am about out of ideas. This is my first diesel and am not a mechanic, but consider myself mechanically inclined. Okay here is the issue:

The truck has a 1997 7.3 mated to the zf5. It idles smooth and accelerates fine in any gear to about 2500 RPM then begins to miss violently. The whole truck shudders like it is running out of fuel, but i have the FPR shimmed and fuel pressure never drops below 60psi or so at any point. If i let off the pedal i can ease it over 2500 rpm but if i put the pedal down too much it begins to shudder and stumble again. In neutral i can rev to redline with no issues.

I have replaced the IPR, CPS, checked fuel pressure and HPOP pressure at all speeds and RPM, visually inspected uppipes and turbo boots for leaks, removed cat, removed VC and checked all injector connections and unplugged each to check contribution. I have removed and inspected every sensor I can find with no luck. This is a constant problem, I have never been able to rev over 2500 under load since i've had the truck and am running out of things to check.

Thanks in advance
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Old 08-05-2012, 04:01 PM
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bump. any ideas??
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Old 08-06-2012, 09:53 AM
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When this happens, what are your EGT's and boost level?
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Old 08-06-2012, 01:34 PM
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I dont have a gauge for egt yet because i dont have a tune. and i dont have a boost gauge either but that will probably the next area i investigate. However if it were low boost wouldn't i be getting thick black smoke?
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Old 08-08-2012, 07:14 PM
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bump. anyone have any thoughts???
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Old 08-09-2012, 10:01 AM
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When it's shuddering is it always in the same gear or does it not matter the gear only the RPMs?
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Old 08-09-2012, 01:16 PM
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i can get to redline in granny gear and like 2700 rpm in second but third fourth and fifth i can only get to 2500 when accelerating without bucking
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Old 08-17-2012, 05:43 PM
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bump bump bump
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Old 05-18-2013, 06:44 PM
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Just mechanically inclined as well. Could it be a balance issue somewhere that load/rpm based the higher the gear the higher the engine load at any rpm so maybe the dampers bad? just a guess to keep everyone brain storming
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Old 05-18-2013, 07:47 PM
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Quote:
Originally Posted by agamble View Post
Hello all,

I have been lurking and using all the helpful threads here since I got my truck this spring, but I have had one major unresolved issue and am about out of ideas. This is my first diesel and am not a mechanic, but consider myself mechanically inclined. Okay here is the issue:

The truck has a 1997 7.3 mated to the zf5. It idles smooth and accelerates fine in any gear to about 2500 RPM then begins to miss violently. The whole truck shudders like it is running out of fuel, but i have the FPR shimmed and fuel pressure never drops below 60psi or so at any point. If i let off the pedal i can ease it over 2500 rpm but if i put the pedal down too much it begins to shudder and stumble again. In neutral i can rev to redline with no issues.

I have replaced the IPR, CPS, checked fuel pressure and HPOP pressure at all speeds and RPM, visually inspected uppipes and turbo boots for leaks, removed cat, removed VC and checked all injector connections and unplugged each to check contribution. I have removed and inspected every sensor I can find with no luck. This is a constant problem, I have never been able to rev over 2500 under load since i've had the truck and am running out of things to check.

Thanks in advance
Is your CEL on? if so, scan and get code, that would help a lot. If you have access to a scanner you can use while driving, even better.
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