Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
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What would we be working on? Make, model, engine size, fuel type, auto or stick, 2 or WD?
I'm working on it, my friend. Please give me a couple of minutes...
OK. Thanks for that and for all the details on your original post - you're the kind of customer us experts like to work with.
Seeing that you have already done everything you could do on the sensor side of things, there are only a few other possibilities left, most prominent being the PCM pulling the trigger a little too soon because it needs recalibration, or an actual engine noise triggering the sensor signal (the latter, most likely cold-start piston slap).
I'm going to ask you to play doctor with your truck. This is what I need you to do; first, go to a parts store and get yourself a Mechanic's Stethoscope. Wait for the following morning and safely put that 'scope right up to the block so it won't move when a helper starts the engine. If you hear those pistons slap, you've found the cause. If there is no engine noise, then the PCM needs to be re-calibrated.
Well, looks like your posting speed is much faster than mine.
The reason I recommend the 'scope test on cold-start is because any potential engine noises will be exacerbated.