Weird rail pressure increase when hot

rocknmj

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Anyone ever seen their rail pressure spike after the intake temperature gets a over 87-89 degrees when the engine is under load and about 1800 rpm or higher? My truck runs perfect for the most part but I have noticed that after the intake temp (engine temp is normal) hits about 87 degrees or higher after a couple of minutes that the rail pressure will go from a normal 12-13k psi cruising with a load (pulling, heavy foot, etc) to 18-19k psi. When it does this the injectors get noisy as heck. As soon as you back out a little, it settles back down to what I consider "normal" rail pressure. No codes, no smoke, no excessive EGT etc. Still has power, boost, etc as well. Just rail pressure SPIKE.

We just got back from a 2700 mile trip and I watched it the entire way. Seems to only happen after the intake temp reaches that majic number of 87-89 degrees for more than a few minutes. If the outside air is cold enough to keep it below that it doesn't do this weird thing and the rail pressure comes up and goes down nice and smooth with pedal position. Normally when I'm loaded (26000 gross) cruising at 60mph it runs right around 12-13k psi.

I cleaned the MAF and the IAT2 sensors but didn't seem to make any difference.

Ideas?

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rocknmj

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What tuning?

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I have been running a gh tune for quite a while. I just reloaded another one last night and I'll see how it does today.

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rocknmj

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Switching to different temp modes (different RP tables)
I guess that makes sense (I remember seeing the multiple "hot" fuel curves), but it seems weird how it will go straight from say 13k psi to 18-19k psi instead of spooling up gradually. I'll just keep watching it, especially as we move into the cooler months ahead. I did also just have a whole new engine bay harness installed that finally fixed another rail pressure issue I have been fighting on and off for the last 10 years! Thanks for the input.

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