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Need help with 931 engine problems

 
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Dutch924-racer  



Joined: 23 Jul 2007
Posts: 961
Location: The Netherlands

PostPosted: Mon May 15, 2017 4:15 am    Post subject: Need help with 931 engine problems Reply with quote

I have a/ some problems with the 931 series 2

When cold: running rough at idle/ low rpm
When warm:
Running nicely, great power
But running lean at cruise(AFR 17-20) and under boost (+/- 14)
Vacuum reading is 13/14 – the vacuum gauge says problem with timing
I checked the timing with a stoboscoop and I can see the ‘dot’ on the flywheel which seems to be good.

The enige is fully rebuild.
Modifications:
951 turbo s and intercooler
Stage 1 camshaft
Forge boost controller
Forge recirculation valve
937 DITC

What direction should I be looking for ?
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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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924-76  



Joined: 05 Jun 2006
Posts: 1190
Location: Ontario, Canada

PostPosted: Mon May 15, 2017 4:25 am    Post subject: Reply with quote

Have you perform a smoke test for vacuum leak?
What is your AFR at idle?
Vacuum gauge should read around 17 at idle.
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1976 924 N/A ROW SOLD
1980 931S
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gegge  



Joined: 27 Jul 2007
Posts: 990
Location: Sweden

PostPosted: Mon May 15, 2017 4:39 am    Post subject: Reply with quote

Check CIS pressures, guessing the WUR.
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Carl Fredrik Torkildsen

924 turbo -81 Carrera GT clone LSD Coilovers
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black with low ET "Phonies"
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morghen  



Joined: 21 Jan 2005
Posts: 7548
Location: Romania

PostPosted: Mon May 15, 2017 4:46 am    Post subject: Reply with quote

WUR
Check the CIS pressures.
Check if injectors are working right.
Check if fuel pump is getting 20 Amps.
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Dutch924-racer  



Joined: 23 Jul 2007
Posts: 961
Location: The Netherlands

PostPosted: Mon May 15, 2017 4:47 am    Post subject: Reply with quote

AFR at idle is 14.5-15.

I haven't checked the fuel pressure yet. Will do that next week.

Injectors are new

What do you mean with check the fuel pump is getting 20amp ?
_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
937 DITC
Fast road camshaft
Forge recirculation valve + boost controller
Back to top
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Dutch924-racer  



Joined: 23 Jul 2007
Posts: 961
Location: The Netherlands

PostPosted: Mon May 15, 2017 5:21 am    Post subject: Reply with quote

just pulled out the spark plugs, the all look black, so they don't look like it is runnign lean
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937 trackday car
Series 2 engine
951S turbo and intercooler
937 DITC
Fast road camshaft
Forge recirculation valve + boost controller
Back to top
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1412
Location: Somerset, UK

PostPosted: Mon May 15, 2017 5:47 am    Post subject: Reply with quote

Can you swap out the AFR sensor and gauge to rule out readout error?
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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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Then www.924board.org/viewtopic.php?t=31252
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morghen  



Joined: 21 Jan 2005
Posts: 7548
Location: Romania

PostPosted: Mon May 15, 2017 5:58 am    Post subject: Reply with quote

recalibrate your wideband sensor and gauge.
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Dutch924-racer  



Joined: 23 Jul 2007
Posts: 961
Location: The Netherlands

PostPosted: Mon Jun 05, 2017 5:49 am    Post subject: Reply with quote

Checked the fuel pressure today with a running engine:

Pump pressure: 6,2 bar (should be between 5,8-6,5) ok
Cold pressure: 1,5 bar (should be between 2,4- 2,8 ) not ok
Warm pressure: 2.0 bar (should be between 3,45-3,85) not ok

Does this means my WUR has not died ?? I haven't checked if it gets 12v yet.


_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
937 DITC
Fast road camshaft
Forge recirculation valve + boost controller
Back to top
View user's profile Send private message
Dutch924-racer  



Joined: 23 Jul 2007
Posts: 961
Location: The Netherlands

PostPosted: Sat Jul 01, 2017 1:28 am    Post subject: Reply with quote

problem solved, the wur was bad, replaced it and all pressures are good now.

AFR is also good at cruise now
_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
937 DITC
Fast road camshaft
Forge recirculation valve + boost controller
Back to top
View user's profile Send private message
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