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| 944 Misfire, also oil pressure https://forums.tipec.net/viewtopic.php?f=25&t=9872 |
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| Author: | Pixie*Porsche [ Wed Nov 10, 2010 9:46 am ] |
| Post subject: | 944 Misfire, also oil pressure |
Hi all, I've got a few running issues with my 944, it's a '85 2.5 8v. 1. The car misfires from cold until it is up to temperature. When it is warm, it's fine and once started again from warm it is fine. This has been a fairly recent problem - started when the temperature dropped! 2. The cars oil pressure is fine when started from cold (nearly 5 bar) and when idling when warm (between 2/3 bar) but when it's running and warm it doesn't seem to want to go above 3 bar, unless over 4500rpm - it will climb to 41/2 bar in the latter stages of the rev range. Thanks in advance, Nicola |
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| Author: | Lowtimer [ Wed Nov 10, 2010 10:02 am ] |
| Post subject: | Re: 944 Misfire, also oil pressure |
What grade of oil are you using? |
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| Author: | Pixie*Porsche [ Wed Nov 10, 2010 11:03 am ] |
| Post subject: | Re: 944 Misfire, also oil pressure |
15w/40 mineral oil. |
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| Author: | Lowtimer [ Wed Nov 10, 2010 11:59 am ] |
| Post subject: | Re: 944 Misfire, also oil pressure |
That's a reasonable weight. I asked because some of the more modern ultra-runny oils can lead to lower pressure figures. It is normal for oil pressure to be lower with the engine hot, and to vary with RPM up to the point where the oil pressure relief valve opens. Oil pressure gauges can vary, especially on cars of this age, so I would not necessarily be alarmed by what you are describing, unless it represents a sudden change from what has gone before. If the behaviour has changed recently - i.e. the pressure at a given RPM is now a lot lower than it was a couple of months ago - then it may be that your oil pressure relief valve spring has weakened, or that the oil pump is showing some wear. Is everything else OK? Oil consumption normal, no sign of oil / water contamination, and so on? |
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| Author: | peanut [ Tue Nov 16, 2010 8:52 pm ] |
| Post subject: | Re: 944 Misfire, also oil pressure |
Nicola your cold running problems could be due to the cold start mechanism. On the early 944 (pre 85.5 non oval dash models ) there isn't a seperate cold start injector. Instead the ECU (engine contol unit ) which controls the fuel injectors increases the pulses to the injectors to supply additional fuel as it does when you accelerate . This pulsing is controlled by the engine coolant temperature sensor which I suspect may be faulty. The sensor is usually located near the front of the cylinder head and contains a thermistor and is easy to test for correct operation using the guide on Clarkes garage workshop manual. They are relativly cheap to replace . There are lots of other componants that can give temperature related faults but this would be a good place to start. |
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