I've noticed the VQ37VHR being very rough for the first 15 or 20 seconds on a cold start. It has NOTHING to do with how high it is idling. I'm pretty sure it has something to do with the VVEL. Nissan has probably programmed it to do something bizarre on cold starts for better emissions. The exhaust note is so rough sounding....and then it just slowly smooths out and sounds fine.
It's also real bizarre that if you tap the gas (even slightly), the engine revs WAY up....and stays at like 3000rpm for a few seconds. Even when letting off the throttle, it still stays revved up there for a few seconds. Again, why I say that it has something to do with how the VVEL/timing advance is programmed to reduce hydrocarbon output from the tailpipe.
Late,
Trav
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