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The Phantom Revver


Well-known member
26 Oct 2002
I have a problem. My car is idleing strangely. Instead of the normal 800 rpm it is revving to 11-1200 rpm and then dropping back to 800 and repeating the cycle, sounds like you are revving the engine. Any ideas anyone?

The only thing I can think is that I may have some dirt in an injector or something. I had taken it for a good blast and should have filled up before the fuel light came on, anyway it was running great up till I refuelled. Help please



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The "filling up with fuel" thing could be a red herring but have you tried changing the fuel filter? May be you dislodged some crap (technical term) that is now blocking the filter?

Sometimes a bad patch of fuel can cause hunting issues. The cheapest fix to try first might be to use all the fuel (or syphon it out) and refill. Did you use a branded fuel or was it a Sainsbury's job (not that a brand is any guarantee of quality)?

Apparently a bad battery can cause erratic idling too. You could try changing the battery or measuring the voltage of the current one.

Also check all you fuses, specifically the one to the "Warm Up Regulator" (WUR) and Auxillary Air Valve. They are used when the car is cold and also affect idling.

Cheers, James

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Thanks James, The problem only occurs when the engine is warm/hot. I phoned the local Porsche centre, they thought it could be a failed sensor on the inlet manifold. BTW they charge £85 per hour labour but they discount this by 25% for older cars like mine. The full 96000/12000 mile service costs £530 inc vat. Strangely this not much more than I was quoted by Autostrausse who are my nearest independent. I'm thinking that maybe a proper main dealer service might be the way to go.

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The fact that is only occurs when it is warm/hot implies that it is the WUR. It would be worth checking the fuse to this first before dipping into your pocket at a garage.

Re independent vs OPC - I understand OPCs are winning back some business with their cheaper rates on older cars. There is a view, however, that they don't really have the knoweldge/skills for the older cars as they are all primarily trained and experienced in the newer cars (996/Boxsters etc).


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blimey that was quick!



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Talking cars is a lot more interesting than what I am doing at work at the moment!

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I'm stuck in my shop till 5pm today, might try and phone the wife and check the fuse over the phone, I will let you know later.


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Hi Keith

sorry to butt in like this, but that is a fair match of a wife you got there if she can check your fuses - I think mine wouldnt even know where the engine was :)))


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:D :D :D :D :D :D :D :D

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Elias makes a fair comment, I flagged the wife idea and bought a cheap torch to see for myself after 5pm. All the fuses in the main box are intact. Unless the WUR fuse is located eleswhere then it seems that this inlet sensor thing is the problem. Mind you it isn't as bad as it was when I refuelled so I will persist with the burning off the old fuel theory for now.



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Hunting idle usually caused by mixture being too rich. My Carrera had this problem last year after mechanic adjusted idle by measuring voltage fluctuation at O2 sensor instead of proper method (exhaust gas analyser).

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The problem has cured itself on mine. Idling fine for the last few hundred miles now. I have it booked in for a full service including valve adjustment next week. I will ask the mechanic to check the idle then.


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