My 1ZZ-FE with 145k miles on it has sounded progressively worse over the past few months, but I'm loathe to pay the $80 "engine diagnostic" fee that my mechanic wants to figure out what's wrong.
I think the problem is with the oil system. It burns oil excessively like many of its brethren, but I keep up with the losses and still get oil changes every ~3,000 miles. When accelerating from stop the engine will "rumble" as if the oil is really low (when I know it definitely isn't), and I can feel it in the gas pedal, but the rumble goes away once the RPMs get up and I'm past about 10 mph. It returns every time I start from a stop. It also will occasionally appear when I start the engine cold and lasts for a maybe a second and a half.
Further, when accelerating either from stop or at speed there is a sporadic tinging that I can hear. It's a very tinny sound (more like a loud ticking) that seems random and non-rhythmic and I'm hoping isn't spark knock.
Neither the oil indicator light nor the check engine light are lit.
Could this be an oil pump problem? Any steps that I can take on my own? Or am I doomed to make an expensive mechanic's visit?
Thanks in advance for any insight.