Elevated Idle

My son and I practice hypermiling with our Subarus - ya know, throw it in neutral to coast down down hills, etc. This yields 2-4 MPG savings.

Both cars have A/Ts, his is a '97 2.5 GT, mine an '04 Forester.

When I go in to neutral to coast, my idle drops down to normal; however Colin's LGT only drops to about 1200 RPM and stays there. Yesterday, I reset the ECM (disconnected the battery, discharged the system) thinking this would sort it out - no change.

It will return to normal idle if I shut down the engine and start it up, so I know there are no vacuum leaks or other such influences.

Thoughts?

whats the idle sitting still? in gear and in park?

Im a mechanic, and not every car i drive drops to base idle while your still moving, so it could be normal.

On a side note, i do the same... pop it in neutral and coast a lot.. especially getting off the highway.. and i thought i was wierd for doing it, maybe im not?.... lol.

High idle is speed related. If I'm going into N from about 35 MPH, idle is normal; when from 50, it's elevated.

Otherwise, idle is normal.

I average 29 MPG or so with hypermiling; it would be better if I kept speeds below 60 MPH, but I don't want to become a hood ornament.

you want / need the trans oil pump moving the fluid in the trans even when you are in N.

it lubes the trans.

the greater the speed,

the greater the need for lubrication.

you want / need the trans oil pump moving the fluid in the trans even when you are in N.

it lubes the trans.

the greater the speed,

the greater the need for lubrication.

...and your point is?

I don't shut down the engine when coasting.

my point is if coasting in N at 25 mph your trans needs some lubrication.

if coasting in N at 55 mph your trans needs more lubrication.

the computer is smart enough to know this,

and adjusts the idle speed accordingly.

the manual trans has the gears rotating in an oil bath.

the auto trans is different, it needs the oil pump to move the lube..

my big complaint with the 00 - 01 auto trans, (probably 00+)

when i let off the gas around town,

it feels like there is engine braking going on.

it never feels like it is completely dis-engaged.

i never feel this on my 95 - 98 cars.

i'm pretty sure they engineered this,

but i don't know why. safety? control? ?????

it seems to me like it would use more gas,

but idk.

i hate getting stuck behind hypermilers... just sayin...

as for the issue, my car is the same way, as is my dodge truck. the truck is a manual trans tho, if i am coming up to a stop i can put the clutch in, and see the idle drop from about 1400 down to normal as i drop below 20mph. at first i thought it was an issue i needed to fix, but it makes sense that it does it on purpose.

i hate getting stuck behind hypermilers... just sayin...

 

as for the issue, my car is the same way, as is my dodge truck. the truck is a manual trans tho, if i am coming up to a stop i can put the clutch in, and see the idle drop from about 1400 down to normal as i drop below 20mph. at first i thought it was an issue i needed to fix, but it makes sense that it does it on purpose.

You won"t get stuck behind us at the gas station.