revs linger

Subafury · Post by **Subafury** » Mon Sep 03, 2007 9:12 pm

just a quick one (hopefully theres a quick answer

)

after i rev my ea82t in neutral it comes back down to like 2500rpm pauses for a split second then goes slowly back down to idle. any suggestions as to what it is? all i can think of atm is the accerator cable spring, but i tried fixing that already.

Matatak · Post by **Matatak** » Mon Sep 03, 2007 9:19 pm

and this has just started happening?
wt do u rev it up to aswell? (just curious

)

check out the Throttle Dashpot as they are wt makes the idles come down slowly
shuld be somewhere around th Linkage on motor for Cable id think

just check it to see wt it does and wtever

(but my posts dont make sense lol)

steptoe · Post by **steptoe** » Mon Sep 03, 2007 9:53 pm

Subi, what sort of revs is idle on yours ? Mine idles at 1200 in Park and drops a bit in Drive or Reverse. More than what specs are and this is measured on a hand held tacho not the poopy slow to return dash tacho!

Subafury · Post by **Subafury** » Mon Sep 03, 2007 9:57 pm

its been happening for ages, im just at the point where i wanna fix niggly little things, or at least know whats causing them.
idle is at 1000-1100 and this is seen thru my aftermarket tacho- my L isnt good enough for an indash one

maybe i should google throttle dashpot to see what one looks like- unless someone can point one out for me.

Matatak · Post by **Matatak** » Mon Sep 03, 2007 10:03 pm

idles a bit high Mr Subi

lol i can point one out (throttle dashpot)

Gannon · Post by **Gannon** » Mon Sep 03, 2007 10:54 pm

Yeah its supposed to do that.
There is a small dash-pot (works kinda like a shock absorber)
Its designed to prevent a boost surge when the throttle is shut quickly. It simply slows the throttle plate just before it closes.
Recirculating BOV's take care of this in more moden turbo cars.

Dont worry, your car was designed to do what its doing.

Subafury · Post by **Subafury** » Mon Sep 03, 2007 11:04 pm

Suparoo wrote:Yeah its supposed to do that.
There is a small dash-pot (works kinda like a shock absorber)
Its designed to prevent a boost surge when the throttle is shut quickly. It simply slows the throttle plate just before it closes.
Recirculating BOV's take care of this in more moden turbo cars.

Dont worry, your car was designed to do what its doing.

ok cool thanks for the info and quick responses

Subafury · Post by **Subafury** » Mon Sep 03, 2007 11:08 pm

Matatak wrote:idles a bit high Mr Subi

lol i can point one out (throttle dashpot)

when it was tuned by rotormotion they said it should idle about 1000rpm
and google images did help- i know what ur talkin about.

Matatak · Post by **Matatak** » Mon Sep 03, 2007 11:10 pm

idle is usually 800 didnt think urs was that special lol

Subyroo · Post by **Subyroo** » Thu Sep 06, 2007 12:18 am

My 03 XS Forester (N/A) does the same thing since the Neutral Switch was replaced at the last service and it drives me insane when it hangs at 1500rpm.

It nearly caused a rear ender one day recently on the way to Brissy in the wet when the traffic was down to stop and go traffic pace.

I've had the car back to the Service Centre and they assured me it was normal and I told them it has never done that in the last 100,000kms of which you have done all but 2 of the Services - why now?
They could not explain it.

discopotato03 · Post by **discopotato03** » Thu Sep 06, 2007 8:28 am

Its an emissions device with early EFI systems . Anyone thats ever tuned a programmable one finds that when the throttle/s snap shut quickly you get a momentary rich mixture , its caused by the fuel in the system can't be shut off as quickly as the air supply so the AFR goes up momentarily . The damper is there to make sure the air supply doesn't drop faster than the rate of injected fuel and you don't get the extra tiny bit of rich emissions .

LOL batch fire systems have issues here because they inject into inlet ports regardless of the valve timing so the unused fuel has to go somwhere . With sequential injection and todays fast ECU's the closed throttle fuel cut is MUCH faster reacting than it used to be and the idle air bypass valve does any "dashpot" function .

Cheers A .

PS if you were to loosen the dashpots locknut and screw it out a little I wasn't looking ....

SCOOBIDOO · Post by **SCOOBIDOO** » Thu Sep 06, 2007 8:51 pm

discopotato03 wrote:Its an emissions device with early EFI systems . Anyone thats ever tuned a programmable one finds that when the throttle/s snap shut quickly you get a momentary rich mixture , its caused by the fuel in the system can't be shut off as quickly as the air supply so the AFR goes up momentarily . The damper is there to make sure the air supply doesn't drop faster than the rate of injected fuel and you don't get the extra tiny bit of rich emissions .

LOL batch fire systems have issues here because they inject into inlet ports regardless of the valve timing so the unused fuel has to go somwhere . With sequential injection and todays fast ECU's the closed throttle fuel cut is MUCH faster reacting than it used to be and the idle air bypass valve does any "dashpot" function .

Cheers A .

PS if you were to loosen the dashpots locknut and screw it out a little I wasn't looking ....

NICE READ TODAY....batch pulse at 2 prescibed point..once when the intake valve is closed and once on the intake stroke....there is never anyunused fuel before the combustion process...think about what your saying..where would it go?????? L serie,s ea82 t,s had fuel cut way back in the 80,s..
anything above 2000rpm without throttle,the ecu cut pulse to the injectors.
so this means they are still up there with the best by your fast standard,s..LOL keep learning..i am...cheers

Suby Wan Kenobi · Post by **Suby Wan Kenobi** » Thu Sep 06, 2007 9:12 pm

dont know weather you have fixed it but remove the slow return dash pot to see if its the cause. (it sounds like ther problem) if it returns quickly then you have found it if not it could be a sticking EGR. PS should idle at 750 warm but if you are offroading it i have found that on an EA engine 1000rpm to be more responsive