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Old 12-22-2007, 10:32 AM   #1
jump454
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Default drop rpms faster?

is there anyway to make the motor drop rpms between shifts? on my vw golf it had a thing on the throttle called a dashpot with held the throttle open when u let off and made it close slowly. some bull**** about emissions. with the car off anf i flick open the throttle on my 98sc1 by hand and release it sounds like their something in their that might do the same thing? can anyone confirm this or tell me how to get rid of it?
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Old 12-22-2007, 10:49 AM   #2
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Default Re: drop rpms faster?

There is no such thing on a Saturn. If the rpms seem to "hang" when shifting, (manual tranny?) you may want to look into a ECTS replacement. Do a search for it.
There is a ton of threads with the same condition you are explaining.
Also look into a cleaning of the throttle body and IAC.

When you flick it open by hand, does the throttle plate stick?
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Old 12-22-2007, 11:01 AM   #3
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Default Re: drop rpms faster?

You may notice days where the RPM does drop really quick. Usually it does not. This has to do with the IAC and conditions. It is for emissions, but perhaps you could find a way to manipulate it. I don't know much about it otherwise.

I know valve timing has the greatest impact, not that the Saturn changes it at all. Ignition timing may affect it too. Basically you need to achieve the most vacuum.
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Old 12-22-2007, 11:56 AM   #4
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Default Re: drop rpms faster?

The IAC does it on these cars. It's actually required to run the car at idle so you can't remove it...but you can get a 4point switch and turn it off while driving (or have your friendly engine gnome unplug it for you).
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The proper way to fix a S-Series automatic is to replace it with a manual
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Old 12-22-2007, 05:29 PM   #5
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Default Re: drop rpms faster?

Have you messed with the throttle position at all?

Last edited by VQ30toLL0; 12-22-2007 at 05:35 PM.
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Old 12-22-2007, 11:29 PM   #6
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Default Re: drop rpms faster?

Quote:
Originally Posted by jump454 View Post
is there anyway to make the motor drop rpms between shifts? on my vw golf it had a thing on the throttle called a dashpot with held the throttle open when u let off and made it close slowly. some bull**** about emissions. with the car off anf i flick open the throttle on my 98sc1 by hand and release it sounds like their something in their that might do the same thing? can anyone confirm this or tell me how to get rid of it?
if you want the engine to drop RPM faster, you'd need a lighter flywheel.
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Old 12-23-2007, 01:18 AM   #7
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Default Re: drop rpms faster?

no it doesnt stick open. so maybe ect is a good idea. that what ive been reading to. but it just seems the throttle blade gets pushed open but when it closes it like attached to a sperate spring or actuator. it all functions correctly but it just drops rev so slow thats all.
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Old 12-23-2007, 01:26 AM   #8
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Default Re: drop rpms faster?

lighter flywheel +1
Using a switch to turn off the IAC, also +1
You could even use a relay so that the IAC only turns on when you press the clutch. YEAH!
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Old 12-23-2007, 03:09 AM   #9
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Default Re: drop rpms faster?

then you stall at stop signs lol
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Old 12-23-2007, 04:38 AM   #10
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Default Re: drop rpms faster?

Quote:
Originally Posted by jump454 View Post
no it doesnt stick open. so maybe ect is a good idea. that what ive been reading to. but it just seems the throttle blade gets pushed open but when it closes it like attached to a sperate spring or actuator. it all functions correctly but it just drops rev so slow thats all.
What fetchitfido and Crewcab were trying to tell you was to look into the throttle body, clean it to degrease the biuld-up in and outside so the throttle plate is free to move w/o sticking. The throttle plate DOES NOT automatically open and close by itself or by computer - YOU are controling the throttle plate movement. However, you may not know that the idle air control valve (IACV) IS under direct control of the PCM to adjust the idle speed during; cold start-up, a/c use, and closed throttle deceleration at speed. The iacv controls the idling speed by opening and closing a bypass air port to regulate idle speed. When the engine is cold the iacv allows a higher idle, up to 1200 rpm, to quickly warm up the engine and gradually lowers the idle speed as the engine warms up until operating temperatures are reached (coolant temps at 195d F.) where the idle is back down to 800-900 rpm. All this in 10-minutes of driving.

When the revs drop too slowly in-between shifts, there are several issues that may be holding the revs up preventing the engine from slowing down; the iacv is sticking a little, the throttle body plate may be sticking from build-up, and the engine coolant temperature sensor failing.

1-The iacv is a precision stepper motor and cleaning should only be done with electronic contact cleaner. Remove it from the throttle body carefully for cleaning. It moves in small steps, in and out, as commanded by the PCM to regulate the idle speed. During shifts the iacv allows the rpm to drop to approximately 1200 rpm, no lower (emissions related), and if the engine doesn't want to drop rpm's quickly, the cause of this may be the iacv or a sticking throttle plate. The throttle plate should be closed (not completely), when your foot released the throttle, and remain closed during the gear shift which is what you're doing correctly. If one or the other is sticking then you have to examine the throttle body and go from there. If cleaning the iacv doesn't drop the rpm as you would expect, then you may have to replace the iacv.

2-The throttle plate closes but remains partially open and should never be adjusted as the iacv does the fine tuning of the idling speed, raises the idle for cold engine warm-ups, lowers it back when the engine is fully up to operating temperature, keeps the high idle during gear shifts, raises the idle a bit to compensate for the a/c compressor load on the engine, and in a manually driven car when coasting in neutral from high speed the idle is kept at 1200 rpm until the speed drops below about 10-15 mph then the iacv closes the bypass air to drop the idle back to 800-900 rpm.

3- The ECTS was mentioned as a precaution if it wasn't repaced. The original plastic sensor cracks and sends incorrect signals keeping the engine either too lean or usually too rich with a higher idle than normal. Replacing the original one with the brass one corrects this problem. The two-wire connector needs to checked for corrosion also and must be replaced if corroded.
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Old 12-25-2007, 01:14 PM   #11
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Default Re: drop rpms faster?

The Hyundai elantras guys have been experimenting with IAC restrictors if you want to read up.

http://www.elantraxd.com/forums/show...light=rpm+hang
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