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AFM #725
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Idle fluctuations
Is it normal for my idle RPM to go down with the A/C turned on and up with it off? This usually changes the RPM by about 50-70 RPM. If my car idles at about 930-950 there is little to no vibration. Sometimes the idle will drop to 880-900 with the A/C on which causes some shaking. When I got the car the idle was set too low and I just went and twisted the screw out a bit. Is that the right way to adjust the idle?
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08-18-2012, 08:02 PM
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Registered User
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My 944 does the same thing when the A/C is turned on.
Haven't looked in into what it may or may not be yet, but I'm working my way to diagnosing it soon though. |
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08-19-2012, 04:50 AM
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Registered
Join Date: May 2010
Location: Erie, PA
Posts: 237
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Have you cleaned you ICV?
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86NA944 |
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08-19-2012, 06:56 AM
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AFM #725
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No, I was wondering about that part. I hear its name, but I don't know where it is or how it works.
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08-19-2012, 12:14 PM
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Registered
Join Date: Sep 2011
Location: Florida
Posts: 1,949
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Quote:
Also iirc when you switch on the AC the DME gets a signal which then raises the idle while the AC is on. I think that is your problem. Hopefully someone will chirp in and confirm this and how to resolve it - it's been a while since I worked on the AC control unit system. btw the ISV is under the intake manifold. |
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08-19-2012, 02:04 PM
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AFM #725
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I was able to locate the idle control valve on the car. Scratching my head though on what to do.
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08-19-2012, 06:07 PM
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Registered
Join Date: May 2010
Location: Erie, PA
Posts: 237
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Remove it and clean with carb cleaner. Just kind of flush it out.
Quote:
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86NA944 |
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08-20-2012, 06:29 AM
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Registered User
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I have a new engine and a fairly new compressor and mine does drop in RPM when I turn it on.
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08-20-2012, 06:39 AM
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AFM #725
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Still have not solved this problem.. lol
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Watchdog Armory Racing AFM #725 Thanks to my 2017 Sponsors: JPH Suspension | AXO | Armour Bodies | BELL Helmets | Braven | EVLUTION Nutrition | Forcefield Armor | FunTrackDayz | Galfer | Motion Pro | MOTUL | Matrix Racing Concepts | ODI Grips | OGIO | Shorai Inc. | SPEEDMOB | Vortex | Woodcraft | Wicked Audio http://www.gawerracing.com |
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03-26-2013, 03:35 PM
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Banned
Join Date: Apr 2011
Posts: 683
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The iacv usually is internally damaged on the commutator contacts, as well as significant loss of the carbon brushes. This is cause they stick, the computer continues to try and get it to move, and the voltage eventually blasts a hole in the commutator surface.
I successfully rebuilt my iacv using hard pipe solder and a bench grinder to resmooth the commutator. I've got tons of pics of the process and really want to post a full guide on how to do it I just have to upload the pics to imgur or something and write it up. |
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03-26-2013, 03:53 PM
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AFM #725
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The thing is my idle is very good without the A/C on. It just goes lower when turning the A/C on and it ends up being a bit random... I did clean the valve out best I could tell with carb cleaner and that seemed to help the sticking that was causing idle surge but still I have to sometimes whack it with my flashlight
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Watchdog Armory Racing AFM #725 Thanks to my 2017 Sponsors: JPH Suspension | AXO | Armour Bodies | BELL Helmets | Braven | EVLUTION Nutrition | Forcefield Armor | FunTrackDayz | Galfer | Motion Pro | MOTUL | Matrix Racing Concepts | ODI Grips | OGIO | Shorai Inc. | SPEEDMOB | Vortex | Woodcraft | Wicked Audio http://www.gawerracing.com |
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03-26-2013, 04:12 PM
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Banned
Join Date: Apr 2011
Posts: 683
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Same thing on my 944 while I still had it. Ac on I had to hold the pedal in at idle to keep rpms up and sometimes it would buck and surge. Sometimes it would go wonky and buck and surge without the ac on too, but that was rare and revving it hard a few times made it stop every time.
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03-26-2013, 04:17 PM
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AFM #725
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I'm just going to adjust the TB adjustment screw and see what happens. I don't have any bucking or surging, idle is pretty stable, it's just at say 850-900 when I would like 950-1000
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Watchdog Armory Racing AFM #725 Thanks to my 2017 Sponsors: JPH Suspension | AXO | Armour Bodies | BELL Helmets | Braven | EVLUTION Nutrition | Forcefield Armor | FunTrackDayz | Galfer | Motion Pro | MOTUL | Matrix Racing Concepts | ODI Grips | OGIO | Shorai Inc. | SPEEDMOB | Vortex | Woodcraft | Wicked Audio http://www.gawerracing.com |
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03-26-2013, 04:18 PM
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Banned
Join Date: Apr 2011
Posts: 683
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If its stable and just idling too low for your taste then yeah, sure that should definitely help. BTW pm me your email and I'll send thru a pic of this tray for you, sorry its taking me so long to get that shipping figure for you I've just gota ton of **** going on and trying to find a job at the same time here.
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03-26-2013, 04:37 PM
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AFM #725
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Turning the adjustment screw about a half to 3/4 turn clockwise seems to have magically smoothed out the idle... And okay
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03-26-2013, 04:51 PM
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Registered User
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Since the high temps here in Cincinnati are still in the 30s, f*** you and your air conditioning problems. ;-)
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1978 924 The Grey Ghost - 18,000 miles and counting 1987 944 Black Betty - Bringing back from years of abuse |
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03-26-2013, 05:53 PM
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Banned
Join Date: Apr 2011
Posts: 683
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ROFL I just drove through blinding freezing rain not even ten minutes ago. Did I mention the 928 is my only car? Yeah, this weather is getting old.
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03-26-2013, 06:05 PM
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AFM #725
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LOL it felt like it was in the 80's with the sun today. So far so good on the idle.
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03-26-2013, 07:19 PM
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1983 Porsche 944
John Paul Jones
1984 Porsche 944
