Hi Russ, Don't worry about engine speed, as have had this before, a scanner problem I think.
I assume this is the Hydraulic injector diesel, 4JX1 engine? If so get engine oil hot, drain & refill with a very high grade 5w30 oil, we use Castrol performance A1.
This vehicle uses a high pressure pump to pressurise the injectors, using the engine oil, it requires about 4000psi to open injectors cleanly. The wrong grade, or old engine oil aeriates & causes a misfire/incomplete spray on the injectors.