Just recently started acting up. Left the truck sit outside for 20mins at oreillys. Started it and after 5shower secs it started idling way down like it was running out of fuel and then picked right back up. Got to work and tried starting it after 30mins. It did the same thing. I let it sit for almost 2hours and when i went to leave for lunch it loped for about 3secs, then ran rough and then idled up and ran fine. No smoke except black. Started doing this today and i havent done anything to the truck to make it do this. Going to drain the water out of the filter. After that i have no idea. Any ideas

 

All I can think of is idle speed. Maybe the screw got loose with of miles of vibrations.
Or maybe injector failure. Try shooting a temp gun at the exhaust manifold ports and look for large temperature differences. Maybe someone else will help...

 

I took a heat gun to the exhaust manifold when i first got the truck. #6 was about 181 #5 was 195 #4 was 174 #1-3 were 155-160

 

Kinda sounds like an air intrusion, what about when the engine is cold?

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Tired VP. Just a guess.

 

Do you still have the factory lift pump or an electric aftermarket pump