Toyota: Fuel mileage 91 octane vs. 87

Philip® wrote: 

I'm not sure as to the specifics, but it has do with with the difference
in volatility. As for heat soak, the Prius isnt too bad, its pretty
cool. Oxygentated, not sure, we disconinued it, but that may have been
compensated for already. They can widen the parameters to avoid this.
The DSM told us a situation where the car (Prius) kept getting a
cylinder missfire code, and was never able to duplicate it. It showed up
while leaving his driveway. Finally, the DSM went to the house and after
starting and driving out, it came on, missfire code. He had a real rough
cobblestone driveway and it would change the speed of the crank enough
to where the sensor picked it up as a missfire. The ECU's (even in your
Corolla) can tell if the crank speed has slowed down after a specific
cylinder has fires, it assumes its a cyl missfire. 

Yes, its a returnless system to reduce evaporative emissions, just like
your Corolla. 


 

MDT Tech® wrote: 

Regardling the crankshaft acceleration measurement after each
cylinder fires; up to what RPM is this effective?

I've noticed that my Corolla will be a little less willing to fire up
.... and then runs minus a cylinder for a few seconds WHEN I let the
car sit for two days in the closed garage. I have not correlated this
with fuel (I always use 87 octane) or extra hot days, or anything
else. It just happens, as if a small bubble of air was at an injector
inlet. MIL light has never come ON.
--

~~Philip

"Never let school interfere
with your education - Mark Twain"

Philip® wrote: 

I'm not really sure, but with our scan tool and its enhanced software
for Toyota, we see it in % percentage. So it will vary depending upon
engine speed. I know 10% will show up as a code. When I'm watching the
missfire data, in a normal running car, its a flat 0% and we are
watching it like this:


MISSFIRE


cyl#1----------------------0%
cyl#2----------------------0%
cyl#3---------------------10%
cyl#4----------------------0%


And this wound indicate some trouble with cylinder #3. If its
consistent, we can look for low compression, if its intermittent,
usually ignition related

 

Yes, you have an injector dribbling some fuel and filling a cylinder
with a little extra. This is normal from time to time. Its done it on
every rig I've owned and the ECU wont set a code yet until its went into
closed loop mode, so right after start up, it wont even be looking for
it. This scenario seems to go away as the injectors wear. Apparently
they seal tighter. Many times, people wont even notice it, only the
mechanically accute ones will like yourself. I have even heard a tap tap
tap on some, almost a hydro lock. Do you get a stong rich exhaust odor,
ie HC's?

MDT Tech® wrote: 

When this situation occurs, YES there is a faint gasoline smell with
the normal exhaust in the first 30 seconds that comes wafting out
from behind the car. Otherwise, no driveability complaints ... OTHER
THAN .... the light "gulp" (momentary flat spot) that ocurrs
transitioning from -coast- to very light acceleration -only- when the
A/C is ON.
--

~~Philip

"Never let school interfere
with your education - Mark Twain"

"Philip®" <net> wrote in message news:<IAR8b.2680$news.pas.earthlink.net>... 

The Atkinson-cycle engine doesn't much care for the burn differences
with the higher-octane gasoline. (Engine misfires are a common error
code for high-octane users who get check-engine lights.)