modestmatt Posted July 14, 2006 Share Posted July 14, 2006 Over the last few months I've caught on to something funny when I don't drive my '06 OB 2.5i for 12 hrs or more... When I start it up and I'm still in park the engine idles high at 1.5 rpms and if I let it sit for more than a day it will idle at 2000. When I put it in gear ® it usually drops down to normal levels but sometimes it will like to reverse fast. Has anyone ever heard of this or expierenced it personally? A friend said it may be the emissions computer or something. Link to comment Share on other sites More sharing options...
pillboy Posted July 14, 2006 Share Posted July 14, 2006 The revs will drop in both our Subarus if you blip the throttle a little after it is running. It is still ugly. Link to comment Share on other sites More sharing options...
modestmatt Posted July 14, 2006 Author Share Posted July 14, 2006 The revs will drop in both our Subarus if you blip the throttle a little after it is running. explain "blip" Is this done in N or D or P Link to comment Share on other sites More sharing options...
mwiener2 Posted July 14, 2006 Share Posted July 14, 2006 the colder the engine, the higher it idles at cold start. Max is 1800rpm. Touching the throttle should drop the idle to about 1300 if it's still cold. Normal warm idle is around 750 My Mods List (Updated 8/22/17) 2005 Outback FMT Running on Electrons Link to comment Share on other sites More sharing options...
mccorry Posted July 14, 2006 Share Posted July 14, 2006 Mine does it as well... normal AFAIK. Link to comment Share on other sites More sharing options...
AWDDAD Posted July 14, 2006 Share Posted July 14, 2006 mine too, I let it idle for a bit than just tap the gas pedal and the rpms will drop down. ...when death calls, Im good. I got caller ID. Link to comment Share on other sites More sharing options...
pillboy Posted July 14, 2006 Share Posted July 14, 2006 Step on the accelerator slightly while it is still in park. It is still ugly. Link to comment Share on other sites More sharing options...
ebpda9 Posted July 14, 2006 Share Posted July 14, 2006 normal. any car will do it Link to comment Share on other sites More sharing options...
AMBIVALENCE Posted July 14, 2006 Share Posted July 14, 2006 I believe it's caused by cold engine/ cold motor oil/ cold everything? Thats how i always believe, and thats how i forgive my brake being so stiff in winter... Link to comment Share on other sites More sharing options...
05silverbus Posted July 14, 2006 Share Posted July 14, 2006 My 1983 Delta 88 did the same thing. Its called fast or high idle. By bringing the R's up slightly at cold temp it will in turn slightly bring the oil pressure up as well. Utilizing the higher oil psi to bath the motor's vital organs because we should all know where the oil likes to hang out when the cars off right. It the factories way of saving thier posterior. Link to comment Share on other sites More sharing options...
mccorry Posted July 14, 2006 Share Posted July 14, 2006 In case you are curious.... the reason that engines run a a slightly higher idle RPM when cold is that the higher flow rate helps to keep the fuel atomized in the intake and combustion chamber. When you first start your car, the oil, coolant, block, pistons, heads, valves, intake, etc. are all ambient temperature (~75F). Gasoline does not atomize or vaporize well at lower temperatures, so the higher flowrate allows for mecanical atomization of the fuel so that it combusts properly. Without it... the fuel could condense and puddle in the cylinder. Old carburated engines did this with the use of a choke. A choke is a plate that closes in the carburator and forces the incoming air through a smaller space. This smaller flow area, in turn, accelerates the flowrate of the air, causing extra turbulence. Late model electronic controlled cars do this with the ECU and idle controls. In addition, our cars also use the tumble generation valves (TGV's) to assist with this atomization of the fuel. Link to comment Share on other sites More sharing options...
05silverbus Posted July 14, 2006 Share Posted July 14, 2006 By any chance do you know what the desired temperature (ie flashpoint) is at which the gasoline is more usable Link to comment Share on other sites More sharing options...
mccorry Posted July 14, 2006 Share Posted July 14, 2006 The flashpoint of gasoline is around -40F... but that is not the issue.... Flashpoint is the minimum temperature at which a liquid will give off enough fumes to combust. This means that at 40 degrees below zero, gasoline will give off enough vapors for them (the vapors) to ignite. What we are really looking at is vapor pressure of gasoline vs. temperature. The boiling point of gasoline is a range that starts around 75-80F. As temperature increases... the partial pressures increase and the vapor pressure goes up. It is not linear, since gasoline is a solvent blend of many different hydrocarbons. For our cars, the injector sprays a fine mist of atomized fuel into the intake air track. At cooler temperatures... this atomized mixture wants to condense and pool in the bottom of the cyliner. The extra turbulence of the incoming air (via the TGV's) keeps it from condensing out.... When the engine warms up... the atomized mixture is more stable since the gasoline wants to vaporize anyway (at least partially). Link to comment Share on other sites More sharing options...
gfxdave99 Posted July 14, 2006 Share Posted July 14, 2006 Mine does the same thing, and i have a gt.. If everything seems under control, you're just not going fast enough. - Mario Andretti Link to comment Share on other sites More sharing options...
05silverbus Posted July 14, 2006 Share Posted July 14, 2006 The flashpoint of gasoline is around -40F... but that is not the issue.... Flashpoint is the minimum temperature at which a liquid will give off enough fumes to combust. This means that at 40 degrees below zero, gasoline will give off enough vapors for them (the vapors) to ignite. What we are really looking at is vapor pressure of gasoline vs. temperature. The boiling point of gasoline is a range that starts around 75-80F. As temperature increases... the partial pressures increase and the vapor pressure goes up. It is not linear, since gasoline is a solvent blend of many different hydrocarbons. For our cars, the injector sprays a fine mist of atomized fuel into the intake air track. At cooler temperatures... this atomized mixture wants to condense and pool in the bottom of the cyliner. The extra turbulence of the incoming air (via the TGV's) keeps it from condensing out.... When the engine warms up... the atomized mixture is more stable since the gasoline wants to vaporize anyway (at least partially). WOW. I am suprised. I wasn't suggesting that this was the issue just tryin' to be a smart a#@. While readin things around here you tend to find quite a bit of "fluf" with out the knowledge to back it up. And I believe DOT places the flashpoint at -47F:icon_wink Link to comment Share on other sites More sharing options...
mccorry Posted July 15, 2006 Share Posted July 15, 2006 Excuuuuuuuuuuuuuuuuuuuuuuuse me! Link to comment Share on other sites More sharing options...
modestmatt Posted July 17, 2006 Author Share Posted July 17, 2006 Talked to a few more people about this...they are not subie owners, but they are auto gurus and retired mech. engineers. They said that even 1800 rpm sounds like too much, just to be warming up. They said something more like 1200 would seem normal. I dunno. Link to comment Share on other sites More sharing options...
SLegacy99 Posted July 18, 2006 Share Posted July 18, 2006 Interesting. never noticed this. Link to comment Share on other sites More sharing options...
mccorry Posted July 18, 2006 Share Posted July 18, 2006 Talked to a few more people about this...they are not subie owners, but they are auto gurus and retired mech. engineers. They said that even 1800 rpm sounds like too much, just to be warming up. They said something more like 1200 would seem normal. I dunno. My 1969 Camaro idles at 1650 RPM when the choke is closed.... that is the factory recommeded setting. Every engine is going to be different. The RPM setting is not important... Link to comment Share on other sites More sharing options...
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