diagnosis help needed: low idle during warming up after sitting

[jwakil]

I'm running out of ideas why the idle on 930 seems to be extremely low (and almost stalling on letting off the gas) when warming up after few days sitting. After warming up it becomes fine. I have looked at my AAR. See the pics below at room temp and, sub freezing. (the pics are taken from different ends so that's why the opening has switched sides). It seems to be opening up as it should (or should it be more open at freezing?). And actually the low idle happens even if it is started on a fairly warm day. If I drive the car and then let it sit for a few hours and I start again, it behaves fine. Just multi-day sittings is when the problem seems to happen.

Anything else I should look at? I remember on my SC there was another device which prevented huge rpm drops when letting off the gas.

room temp


sub freezing

[stlrj]

It needs to be adjusted to look more like the frozen version but at room temp:



You'll need to tap the round pin in back to get the right opening. From there, it's a matter of trial and error until you get it to where you like.


Cheers,

Joe

[jwakil]

Originally Posted by stlrj

It needs to be adjusted to look more like the frozen version but at room temp:



You'll need to tap the round pin in back to get the right opening. From there, it's a matter of trial and error until you get it to where you like.


Cheers,

Joe

Really? My understanding is at room temp it should be almost closed? Is there a procedure for adjustment?

[Jeff NJ]

I thought the vacuum limiter was responsible for engine speed dropping too quick. I am working on getting mine piped in with my new IC and Chris at Turbokraft told me that by pinching off the vacuum line to the vacuum limiter, it will act as though it isn't installed and RPM drops will be much quicker when off the gas. Maybe that line is blocked or leaking or the vacuum limiter is somehow busted?

Pic of vacuum limiter:

[T77911S]

the part above is a decel valve(DV). it holds the RPM's up and lets them come down slowly when you let offr the gas. i removed mine completely and pulled the pipe out of the intake and plugged the intake. i now use the port on the IC for my diverter valve dump back to the rubber intake elbow.

i have not done much with AAR's. i would put power to it, at room temp, just to see if it closes more. first i would spray some carb cleaner in there to make sure it is clean. i think some people have taken them apart and bent the vane inside to open it more.

i would check fuel pressures. bad cold pressure can make it run bad when cold. also check for air leaks.

[stlrj]

Originally Posted by jwakil

Really? My understanding is at room temp it should be almost closed? Is there a procedure for adjustment?

Closed when engine is warmed up, open when engine is cold. A hammer with a suitable bolt is my method. Keep tapping until it opens. If you go too far, turn it over and tap it the other way.

[jwakil]

Originally Posted by stlrj

Closed when engine is warmed up, open when engine is cold. A hammer with a suitable bolt is my method. Keep tapping until it opens. If you go too far, turn it over and tap it the other way.

Which pin do I tap?

[jwakil]

Originally Posted by T77911S

the part above is a decel valve(DV). it holds the RPM's up and lets them come down slowly when you let offr the gas. i removed mine completely and pulled the pipe out of the intake and plugged the intake. i now use the port on the IC for my diverter valve dump back to the rubber intake elbow.

i have not done much with AAR's. i would put power to it, at room temp, just to see if it closes more. first i would spray some carb cleaner in there to make sure it is clean. i think some people have taken them apart and bent the vane inside to open it more.

i would check fuel pressures. bad cold pressure can make it run bad when cold. also check for air leaks.

The power would close it, not open it, so that is not my problem. I already tried spraying lubricant and making sure it was loose. No change. I remember the decel valve on my SC, but I don't think it exists on my 930. I don't see it on the engine .

[stlrj]

Originally Posted by jwakil

Which pin do I tap?

Either end and observe how the opening changes. After 5 mins. you will be the expert...guaranteed!

[T77911S]

Originally Posted by jwakil

The power would close it, not open it, so that is not my problem. I already tried spraying lubricant and making sure it was loose. No change. I remember the decel valve on my SC, but I don't think it exists on my 930. I don't see it on the engine .

yes but that would verify that it closes/works, even though it would be more.
then you could try opening it up more for cold startup.


another thing you can do and i dont agree with how porsche ran the vacuum lines to the dist.
porsche ran the vac advance line to a thermo time valve (TTV) located on the back of the engine case. it is there as they say to prevent advance until the engine warms up. what it also does that is REALLY bad is it blocks boost to retard the timing until the engine warms up which is worse.
i ran my vac retard line to the TTV. that increases the timing when cold to rasie the RPM's just a little more. my vac advance runs direct to the dist.

[stlrj]

Originally Posted by T77911S

another thing you can do and i dont agree with how porsche ran the vacuum lines to the dist.
porsche ran the vac advance line to a thermo time valve (TTV) located on the back of the engine case. it is there as they say to prevent advance until the engine warms up. what it also does that is REALLY bad is it blocks boost to retard the timing until the engine warms up which is worse.
i ran my vac retard line to the TTV. that increases the timing when cold to rasie the RPM's just a little more. my vac advance runs direct to the dist.

That's why all new car engines are all purposely sealed up and impossible to access, in order to keep the owners, who think they know more than the mechanical engineers who designed them, from tampering with them thereby increasing emissions with no real performance gains. Try that on an OBD II car and treat yourself to an instant check engine light.

Also keeps the smog police on their toes.


Cheers,

Joe