Chevy pu 5.3 4x4 when 1st starting out cold you can't get up over 1500 rpms or engine will cough and sputter if you baby it along till it warms up runs great! If you mash the throttle down till it chokes and backfires it will throw a p0336-crankshaft position sensor code. don't know if this is the problem or a by-product of the sputter/backfire, changed fuel filter no help clnd inside of throttle body with carb clnr no help.
I have same problem, Chevy told me it was probably a seal affecting fuel air ratio and when warm seal expanded to stop air leak. I forget which seal but they also said to check plastic case around seal because it will warp and may also need to be replaced. It was located near top center of engine. Please let me know if you figure it out.
What is the fuel pressure reading, sounds like low fuel pressure, you should have 60 PSI at idle and more when you throttle the engine up about 65 PSI, it should NEVER go down.
Testimonial: "I will have to have someone check my fuel pressure. I don't have the equipment to do that."
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I checked the quick way by having the engine running and sprayed carb clnr all around intake and vac hoses no change in rpms
check for vacuum leaks
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