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 Post subject: Heeeeeellllp! My 3.2 engine keeps cutting out...
PostPosted: Wed Nov 14, 2018 3:36 pm 
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This is my first ever post so forgive my inexperience. I have an '87 3.2 Carrera Sport with 204K on the clock - the engine was rebuilt last at 170K. Sometimes it will run for 40 or 50 miles without issue, other days it will not go more than 100 yards without cutting out. It will stall on the drive when cold, it will cut out at any speed under load or not. Every time, I wait up to 30 seconds and it will restart on the key - often accompanied by a huge backfire. Here is what I have done so far to no avail...
- New ICV
- Replaced single wire CHT with new 2 wire
- Replaced air flow meter (reconditioned unit)
- Fixed vacuum leaks
- New auxiliary air Valve
- Refurbed injectors
- New coil
- New fuel pump
- New DME (Porsche OEM)
- New ignition leads, distributor cap and rotor arm
- Fuel injection set to factory settings by Bosch specialist
- Checked earths

Could the fuel pressure regulator be causing my problem (Over-fuelling)? Or an old imobiliser? Or the flywheel sensor? Or reference sensor?

I'm about ready to donate the car to the circus or roll it into a lake, so if anyone knows of a guru in the Bristol area or has some experience with a similar problem I'd welcome any feedback.

Thank you!


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 Post subject: Re: Heeeeeellllp! My 3.2 engine keeps cutting out...
PostPosted: Wed Nov 14, 2018 6:07 pm 
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Joined: Sun Nov 04, 2007 8:43 pm
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Location: Chatham, Kent
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OK you need to be methodical when it cuts you need to know whether fuel or sparks. I sounds to me like it could be a flywheel sensor, not necessarily bad but a bad connection or a fractured wire in the loom.

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Jim

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2005 Porsche Cayenne S
2000 Jeep Grand Cherokee Now sold!
2010 Mazda MX5 Mk3.5 2.0 Sport Tech
2000 Porsche Boxster S SOLD!
1987 Porsche 944 2.5


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 Post subject: Re: Heeeeeellllp! My 3.2 engine keeps cutting out...
PostPosted: Wed Nov 14, 2018 6:21 pm 
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Thanks Jim, I have a new one ready to fit so that's an easy decision. The one in there looks quite new though so I have low expectations. Seems like spark to me due to the backfire, is there a way to know for sure when the problem happens? I only get a 20-30 second window before the car will restart and it always starts first time from cold.


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 Post subject: Re: Heeeeeellllp! My 3.2 engine keeps cutting out...
PostPosted: Wed Nov 14, 2018 7:57 pm 
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Joined: Sun Nov 04, 2007 8:43 pm
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Could be the sensor we have had a few fail on 944s which use a Similar system, but the surrounding wiring looms have also been intermittent on some cars.
Quick question, does the recounted drop very quickly as it cuts out?

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Jim

http://tipec.net/region_southeastlondon.php

2005 Porsche Cayenne S
2000 Jeep Grand Cherokee Now sold!
2010 Mazda MX5 Mk3.5 2.0 Sport Tech
2000 Porsche Boxster S SOLD!
1987 Porsche 944 2.5


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 Post subject: Re: Heeeeeellllp! My 3.2 engine keeps cutting out...
PostPosted: Wed Nov 14, 2018 8:46 pm 
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Not sure but I don’t think so. Most of the time it happens when I come off the throttle and everything seems normal until you go to accelerate again. All gaihes continue to work and the ignition lights come on as I dip the clutch.


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 Post subject: Re: Heeeeeellllp! My 3.2 engine keeps cutting out...
PostPosted: Fri Nov 16, 2018 5:32 pm 
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OK, I replaced the flywheel sensor and it started right up, ran for 45 seconds or so and died. Now it won't start at all. I check resistance at the ECU plug, flywheel and reference sensors read 998 ohms but when you crank the engine over I am seeing zero volts coming from both. CHT sensor measures 3,000 ohms when cold. Changed the DME relay (which was new), it started up for about the same amount of time and ran badly, then died. After 30 seconds or so of rough running, the CHT was reading 1,400 ohms.

I double checked the flywheel sensor gap and it's 0.8mm. Could the reference sensor be the cause of the problem?


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 Post subject: Re: Heeeeeellllp! My 3.2 engine keeps cutting out...
PostPosted: Fri Nov 16, 2018 5:43 pm 
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Location: Emsworth Hants
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Give Eddie at Silvertune a call, and explain your issues...he is in Christchurch and is an air cooled guru.

Call him on 07702465926 Tell him Steve Wagg suggested you call him, he will sort your problem.


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