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finnystew

Violent shuddering after 10 mins of driving

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After tackling at over fuelling issue in my 944s I have now run into something else.

I drive the car for 10 mins and it starts to jerk violently and consistently back and forth, particularly on acceleration at speed in 3rd and 4th. If I shift into another gear it goes away for a second and then comes back. The engine is prone to stalling when it’s like this

Could it be the clutch slipping and rengaging? A leak on the pressure plate? Slave cylinder? Drive train?

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Sounds like a fuel supply issue. Check that your fuel pump is working properly. Good connection, earth etc. Or shit in the tank blocking outlet.

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16 hours ago, finnystew said:

After tackling at over fuelling issue in my 944s I have now run into something else.

I drive the car for 10 mins and it starts to jerk violently and consistently back and forth, particularly on acceleration at speed in 3rd and 4th. If I shift into another gear it goes away for a second and then comes back. The engine is prone to stalling when it’s like this

Could it be the clutch slipping and rengaging? A leak on the pressure plate? Slave cylinder? Drive train?

Just a long-shot guess - Take the petrol cap off & see if it runs OK, it might be build up of vacuum in the fuel tank ???? 

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18 hours ago, Airhead said:

Sounds like a fuel supply issue. Check that your fuel pump is working properly. Good connection, earth etc. Or shit in the tank blocking outlet.

Getting solid pressure reading around 3.6 in the garage cold and warm. It only happened when I’m taking it for a drive.

15 hours ago, 944s2cab said:

Could be a sensor,

So far tested AFM, TPS and NTC which all seem okay. Could be a different story once they warm up. I’ll check grounds next

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I had a REX and it did exactly the same thing, eventually tracked it back to a intermittent fault in the immobiliser.

Threw the piece of shit away.🙂 

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1 hour ago, The Caretaker said:

I had a REX and it did exactly the same thing, eventually tracked it back to a intermittent fault in the immobiliser.

Threw the piece of shit away.🙂 

The car or the immobiliser?? .. :Chuckle2:

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19 hours ago, Dreamr said:

The car or the immobiliser?? .. :Chuckle2:

Definitely not the car! loved that thing, heaps of fun. 

Especially after it went to Al at Gotitrex in Sunshine for a tune and some goodies. :LOL:

The immobilisers were put on the OZ delivered cars after they arrive. I believe to appease the insurance companies as these cars were over represented in their theft payouts.                      The immobilisers were notorious for shitting themselves, they had a hijacking component which had the ability to shut down the electrics and leave you stranded.:Sweating:

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23 hours ago, The Caretaker said:

I had a REX and it did exactly the same thing, eventually tracked it back to a intermittent fault in the immobiliser.

Threw the piece of shit away.🙂 

The car does have an aftermarket immobiliser. However the bucking only happens after 10 mins of driving. It can sit in the garage warming up for 15+ mins happily. Also a light comes on when the immobiliser is enabled (which I haven’t noticed).

On 20/06/2019 at 18:21, Airhead said:

Sounds like a fuel supply issue. Check that your fuel pump is working properly. Good connection, earth etc. Or shit in the tank blocking outlet.

getting a consistent 3.6 bar of fuel in the garage.

could be grounds getting shaken out

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On 21/06/2019 at 12:53, finnystew said:

Getting solid pressure reading around 3.6 in the garage cold and warm. It only happened when I’m taking it for a drive.

So far tested AFM, TPS and NTC which all seem okay. Could be a different story once they warm up. I’ll check grounds next

No shaking goin' on in the garage (depending on the tunes on the radio). Grounds could be loose but still on the terminal.

 

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TPS checks out according to Clark’s garage specs. Wiring to DME is also okay.

 Could be a different story while driving?

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34 minutes ago, AD911S said:

How long ago was the fuel filter replaced ?? Pressure and flow are different things 

Nothing in previous owners history. Worthwhile doing that

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Yes  fine silt blocks the flow so car run fine at low revs but the filter get blocked as the flow increases . If you stop wait 5 min then take off again does it run fine for a while then starts missing again  

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13 hours ago, AD911S said:

Yes  fine silt blocks the flow so car run fine at low revs but the filter get blocked as the flow increases . If you stop wait 5 min then take off again does it run fine for a while then starts missing again  

Yes I can stop for a while and it will behave but then reappear. But this only works a couple times with diminishing return so getting back to the garage becomes a race against the clock.

Also worth mentioning that i have a misfire on cold starts that fades away somewhat when it warms up.

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AFM potentiometer tested with the help of Clark’s garage. All good. Cleaned the contact strip  anyway

I’ve ordered a ryco replacement fuel filter. Tonight I tried to get the old one off... boy is that fitting seized. Even got under the car for better leverage to no avail. Makes me think this filter hasn’t been changed in a long time.

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When you get the old filter off block the inlet and outlet and shake then pour into glass jar if it looks like coffee thats a problem if clear keep looking 

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Succeeded in taking the skin off my hand but not the fitting. Tried heat gun and hammer but you really can’t give it a good whack in its position. Considering taking out the fuel line from the next connection point or cutting the hose.

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On 22/06/2019 at 14:21, finnystew said:

The car does have an aftermarket immobiliser. However the bucking only happens after 10 mins of driving. It can sit in the garage warming up for 15+ mins happily. Also a light comes on when the immobiliser is enabled (which I haven’t noticed).

getting a consistent 3.6 bar of fuel in the garage.

could be grounds getting shaken out

Again not pushing the point, but with the REX it wasn't until you put the car under load you notice it. Being intermittent and eletrical, the lack of current to the fuel pump would be enough to cause it to starve and shudder when it was having it's hizzie fit.

Otherwise perhaps try just swapping out the fuel pump, somone may have one they can vouch for and would be happy to let you borrow for the exercise.

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Finally got the filter out tonight after heat, bang, wrench, repeat. 

As @AD911S said, the fuel inside the filter was black like a double espresso. Also the filter was made in Israel for the 928, seems unusual. New one arrives tomorrow. In the mean time I’m going to test the function of the ISV.

 

023DF00E-5654-426C-A0CD-2E28E4615022.jpeg

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Idle control valve seems to be broken- Or at-least clogged with gunk. It wont open with voltage applied but rather stays 4/5ths shut. Unfortunately you cant disassemble the later ones so i will keep trying to clean it from the outside. Might be up for a new one since this could explain my rough cold starts. 

UPDATE: Cleaned the ICV and it is functioning. Few.. Ill put it all back in tomorrow including the fuel filter and hope for the best

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