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Idle setting problem on 931 S2 ROW UPDATE + VIDEO

 
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Dutch924-racer  



Joined: 23 Jul 2007
Posts: 993
Location: The Netherlands

PostPosted: Fri Jun 30, 2017 5:45 pm    Post subject: Idle setting problem on 931 S2 ROW UPDATE + VIDEO Reply with quote

I tried to adjust the idle on my 931 S2 ROW.

The manual says you put the inletmanifold sensor behind the fire wall en use a stroboscope and adjust untill you see the dot on the flywheel in the reference adge.

But I got the screw all turned to the right, and can't get in further. But I don't see the dot.
If I put the sensor back in the manifold I do see the dot appear.

Am I doing something wrong ?
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937 trackday car
Series 2 engine
951S turbo and intercooler
937 DITC
Fast road camshaft
Forge recirculation valve + boost controller


Last edited by Dutch924-racer on Sat Jul 22, 2017 4:29 pm; edited 2 times in total
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morghen  



Joined: 21 Jan 2005
Posts: 7764
Location: Romania

PostPosted: Fri Jun 30, 2017 6:27 pm    Post subject: Reply with quote

There is a clear procedure, yes...but I'm lazy and just turn that air screw until the RPM suits me and don't disconnect anything....has worked like this for many years.
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1522
Location: Somerset, UK

PostPosted: Fri Jun 30, 2017 11:39 pm    Post subject: Re: Idle setting on 931 S2 ROW Reply with quote

Dutch924-racer wrote:
I tried to adjust the idle on my 931 S2 ROW.

The manual says you put the inletmanifold sensor behind the fire wall en use a stroboscope and adjust untill you see the dot on the flywheel in the reference adge.

But I got the screw all turned to the right, and can't get in further. But I don't see the dot.
If I put the sensor back in the manifold I do see the dot appear.

Am I doing something wrong ?


Did you block the hole when you removed the sensor?

Agree with Morghen. Adjust the air bleed screw on the throttle body to get the best idle speed
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1980 931 - forged pistons, Piper cam, CGT turbo, 951 ducted FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife LSD
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Dutch924-racer  



Joined: 23 Jul 2007
Posts: 993
Location: The Netherlands

PostPosted: Mon Jul 03, 2017 2:06 am    Post subject: Reply with quote

yes I blocked the sensor.

The problem is the engine runs 1500 rpm at idle and the scre is al turned in.

If I pull the conector of the temperature senor on the inlet manifold it runs nicely 900 rpm

Could the sensor be broke, is there a way to test it ?
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937 trackday car
Series 2 engine
951S turbo and intercooler
937 DITC
Fast road camshaft
Forge recirculation valve + boost controller
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morghen  



Joined: 21 Jan 2005
Posts: 7764
Location: Romania

PostPosted: Mon Jul 03, 2017 5:31 pm    Post subject: Reply with quote

yes, it has to have a certain impedance...do you have a Haynes manual?
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Dutch924-racer  



Joined: 23 Jul 2007
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Location: The Netherlands

PostPosted: Tue Jul 04, 2017 5:16 am    Post subject: Reply with quote

I found this in the manual, so it coul aslo be the TPS

If the temperature sensor fails or the wire is pulled off, the ignition timing will be retarded. Also when making idle adjustments, make sure sensor temperature is below 60 C (120 F) (see idle adjustments).

If the throttle switch fails or a wire is pulled off, there will be no ignition retard during starting or coasting, and the idle speed will be too high.

test the intake air temperature sensor with an ohm-meter. Remove it and heat it to 50C (122F) - it should read between 1500Ω-1830Ω. (It can be heated in water or by a hair dryer.) -And if you're willing and able to test again at a higher temp, right at 100C (212F) it should read between 280Ω-350Ω.
at 20C(68F), it should read between 4.5kΩ and 5.5kΩ
at 25C(77F), it should read between 4.2kΩ and 5.2kΩ
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937 trackday car
Series 2 engine
951S turbo and intercooler
937 DITC
Fast road camshaft
Forge recirculation valve + boost controller
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Dutch924-racer  



Joined: 23 Jul 2007
Posts: 993
Location: The Netherlands

PostPosted: Sun Jul 09, 2017 5:37 am    Post subject: Reply with quote

I still have a high idle, about 1250 on a warm engine. Th idle screw is all turned in so no lower adjustment possible.

I checked the timing, the dot on the cam and Z1 on the flywheel are nicely aligned

I found this picture on the board, If I check at idle with a warm engine is is abouw 8 degree beford tdc, is that ok ? The flywheel markings are not visable at idle.



If I folow the idle adjusment procedure: https://www.porscherepair.us/porsche-924-turbo/info-yij.html I can't see the dot on the flywheel at any time.

I did notice when I push the throttle by hand with force backwards, idle will drop. Could the throtthe body be worn or is that normal ?
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937 trackday car
Series 2 engine
951S turbo and intercooler
937 DITC
Fast road camshaft
Forge recirculation valve + boost controller
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1522
Location: Somerset, UK

PostPosted: Sun Jul 09, 2017 7:49 am    Post subject: Reply with quote

Is the throttle butterfly closing completely? Could be letting air through.

Also the seals on the shaft can crumble and let air in. Dan sells a rebuild kit.
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1980 931 - forged pistons, Piper cam, CGT turbo, 951 ducted FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife LSD
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Dutch924-racer  



Joined: 23 Jul 2007
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Location: The Netherlands

PostPosted: Sun Jul 09, 2017 4:27 pm    Post subject: Reply with quote

I turned the thorttle stop screw all the way back, so that could not be the problem, just curious if it alway be open a bit for idle ?

Can anybody test it on his car if you put your throtthle backwards by hand idle wil drop a bit
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937 trackday car
Series 2 engine
951S turbo and intercooler
937 DITC
Fast road camshaft
Forge recirculation valve + boost controller
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1522
Location: Somerset, UK

PostPosted: Mon Jul 10, 2017 4:57 am    Post subject: Reply with quote

Throttle stop screw shouldnt be touched. If you back it off it allows the butterfly to over rotate, it becomes open and allow air past. Pull the boost tube and check if it remaining open by not closing fully or over rotating and reopening.
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1980 931 - forged pistons, Piper cam, CGT turbo, 951 ducted FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife LSD
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Dutch924-racer  



Joined: 23 Jul 2007
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PostPosted: Sat Jul 22, 2017 6:56 am    Post subject: Reply with quote

Update:

I adjusted the mixture leaner and the idle dropped. I was now also able to see the 'dot' on the flywheel when following the idle setting procedure
At idle the mixture is now is lean about 16-18. But when driving is is all fine. Sprak plugs look good also.

The 924 now idles about 800 rpm.

The only doubt I now have is my vacuum, see vidoe below.

Could this be my stage one cam (Intergal profile) or another problem ?

https://youtu.be/zg0LAZE1M-0

https://youtu.be/zg0LAZE1M-0
_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
937 DITC
Fast road camshaft
Forge recirculation valve + boost controller


Last edited by Dutch924-racer on Sat Jul 22, 2017 4:29 pm; edited 1 time in total
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ideola  



Joined: 01 Oct 2004
Posts: 15487
Location: Woodstock IL

PostPosted: Sat Jul 22, 2017 7:41 am    Post subject: Reply with quote

Yes, could be cam, the more aggressive profile can definitely affect idle.
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Carrera RSR  



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Location: Somerset, UK

PostPosted: Sat Jul 22, 2017 7:11 pm    Post subject: Reply with quote

I run 1000rpm with lightened motor and fast road cam. It will idle at 800 no problem but feels too low. At 1000 it idles far smoother and seems kinder to the motor
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1980 931 - forged pistons, Piper cam, CGT turbo, 951 ducted FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife LSD
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Dutch924-racer  



Joined: 23 Jul 2007
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Location: The Netherlands

PostPosted: Sun Jul 23, 2017 12:18 am    Post subject: Reply with quote

Steve, did you ever test with a vacuum gauge ?

With the 800rpm idle the stroboscoop gives TDC on the back of the camshaft gear.
_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
937 DITC
Fast road camshaft
Forge recirculation valve + boost controller
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1522
Location: Somerset, UK

PostPosted: Sun Jul 23, 2017 6:44 am    Post subject: Reply with quote

Never run a vacuum test.

I also wouldnt idle at 16-18 afr. Mine fluctuates between low 14s and 15. Usually bang on 14.6-7.
_________________
1980 931 - forged pistons, Piper cam, CGT turbo, 951 ducted FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife LSD
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252
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