98' just crossed 150k miles and I've started to notice some things with the engine. Owned the car for 4 years, I've never done any work to the motor other than a timing belt. No idea of previous work that's ever been done to the car except a starter motor in 2015. If I had to guess, the major items are probably original.

Cold starts when temps are below freezing are getting a bit rough. The starter motor cranks the engine perfectly, but it seems like it has to crank a couple more times than normal before the engine catches. Instead of da-da-da-vroom; it's da-da-da-da-da-da-daaaa...-vroom

Also, for the first ~10 seconds of these below freezing cold starts, the RPM's jump around a bit. You can hear it bouncing +100 revs, -100 revs, oscillating about once a second.

I also get a very very faint smoky\spicy\weird odor from the exhaust for these same first 10 seconds in my garage, after which it just smells like normal exhaust.

I've noticed this behavior starting to grow over time. It did not have the smelly smoke or the jumpy RPM's in previous years when it's cold started below freezing.

After these 10 seconds, the car seems to operate completely normally. No weird shifting, no faint smell in the exhaust, no lack of power, no rough motor, clean idle.

The car has never leaked a drop of oil from anywhere. However, my fuel economy has become a bit worse over time. I did a road trip recently and was seeing ~23mpg of pure highway driving @80mph. I've seen 25-27mpg on similar trips I've taken. No major elevation gain\loss or serious head\tail winds.

Something I should be concerned about? Or continue to wait until more things develop. My intuition here is there may be an issue that's just beginning to develop and these are early signs. Valve guides? MAF? Sticky throttle? Or something more sinister?

Looking for some knowledgeable input from you guys who know more about this than I. Are there some things I should investigate?

Thanks!

 

Try looking into your PCV system. I replaced the hose, grommet and PCV valve and my idle is pretty smooth now. Before, my PCV hose was about 60% clogged with carbon deposits and the seal from the PCV valve to grommet was a little loose, as well as the PCV hose was cracked on the end. Should be able to buy everything at the Toyota dealer, aside from the molded PCV hose that's Lexus specific. But total was <$35 for everything.