Fiddling with Civic Idle

[arz]

Been playing around with the new (to me) car, getting used to it and such, and noticed something that makes sense from an OEM point of view, but not from a squeezing the every mile out of a gallon of gas.

When I depress the clutch, brake and come to a stop, it will idle at 1500 or so for a few seconds, then drops down to 600ish. Or, coasting down a hill, taken out of gear, it will continue to idle at 1500. Not until I come to a stop for a few seconds will it drop to a normal idle speed.

Talking this over with a handful of car guys I know point that this is probably by design. Keep enough vacuum to have the PB and PS work. Ok, I get that.

Is there a way around this, to have it run at normal idle while coasting? Initial thought says yes, need to figure out the vacuum setup, and apply vacuum (electric pump plus canister) to where ever the sensor is that keeps it in high idle. Maybe even plumb that same vacuum source into the PS and PB system with the use of a one-way valve to draw vacuum as needed.

Or has this all been done and my searching has been lackluster?

[oil pan 4]

Don't bother with the electric pump. A canister and check valve will be more than enough assuminig your civic did not leave the factory with them.

If you let off the gas for just a fraction of a second and allow the transmission to spin the engine with the throttle closed I would expect to see it develope at least 27in/Hg. If you could store that in a vacuum tank you will be all set to run vacuum assisted brakes.

The OEM may have found it cheaper to just fiddle with the ECU progeram to help run brakes insted of installing a tank and valve.

[OG VX]

I was running the exact same thing today while driving my VX.

Thanks for posting. Looking forward to any more replies/insight...

[arz]

A bit more reading today, and this seems to be a very common issue. One "expert" article even indicated that there really isn't a fuel loss from keeping the transmission engaged as the momentum will keep the engine running and not the fuel. Said they had oscilloscope readings across the injectors to show they basically weren't firing. (sounds like bunk to me though).

[j12piprius]

Originally Posted by arz

A bit more reading today, and this seems to be a very common issue. One "expert" article even indicated that there really isn't a fuel loss from keeping the transmission engaged as the momentum will keep the engine running and not the fuel. Said they had oscilloscope readings across the injectors to show they basically weren't firing. (sounds like bunk to me though).

Do you have a link to the article?

[oldtamiyaphile]

Is it the clutch or brake that gives the high idle? or only when both are depressed?

Regardless, all you have to do is remove the relevant switch(es). The clutch switch isn't needed (bypass the starter interlock if so equipped), and you can also wire in a separate switch to run the brake lights. Simple.

[oldtamiyaphile]

Originally Posted by oil pan 4

Don't bother with the electric pump. A canister and check valve will be more than enough

Where would one find such a beast?

[arz]

Originally Posted by oldtamiyaphile

Is it the clutch or brake that gives the high idle? or only when both are depressed?

Regardless, all you have to do is remove the relevant switch(es). The clutch switch isn't needed (bypass the starter interlock if so equipped), and you can also wire in a separate switch to run the brake lights. Simple.

High idle when coasting. Out of gear, clutch in or out. Then I brake to come to a stop, and it continues to at 1500rpm until I've been at a complete stop for about 3-4 seconds. Then it drops to approx 600.

When idling at 600, unless I start moving, it stays there regardless of brake or clutch pedal action. Have not tried idling at 600, then rolling to speed - I'll give that a try later today.

Originally Posted by oldtamiyaphile

Where would one find such a beast?

NAPA or your favorite friendly neighborhood auto parts store.

[arz]

Originally Posted by johnlvs2run

Do you have a link to the article?

Coasting in Neutral or Gear to Save Gas - Coasting and Fuel Economy - Popular Mechanics

[Fat Charlie]

Originally Posted by arz

...there really isn't a fuel loss from keeping the transmission engaged as the momentum will keep the engine running and not the fuel. Said they had oscilloscope readings across the injectors to show they basically weren't firing. (sounds like bunk to me though).

It's bunk. The injectors aren't firing, true, but I'd rather use my momentum for moving forward instead of spinning things that don't need spinning. Engine braking is engine braking: burning momentum is the same thing as burning gas.