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DannyHoffman
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Well guys, a new hip stopped play for a few weeks. Hope you're not still on the edge of your seats....... Fitted the new left pump today, filled up and drove about 15 miles - without a stutter. So it seems like it's finally fixed. Trying to come up with theories to explain the symptoms: 1) Assuming my pump was a touch weak, after a night on the trickle charger maybe the voltage was marginally higher, enough to overcome the weakness? 2) Again assuming my pump was a touch weak, does a full tank put more load on the pump maybe because the pressure on the regulator return is greater as there is more fuel to move around? Thanks for all your help and have a great holiday!
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Filled up today, still running on the left pump only and drove about 6 miles, it ran perfectly. Then I tested the pressure and the gauge needle, whilst at 4 bar, was jumping around a bit constantly. I switched to the right pump and the needle was rock solid. I then swapped the relays and the problem stayed with the left pump. Looking more and more like the left pump.
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Fuel pressure tester arrived today. I've just over 1/4 tank full, and both pumps tested perfectly. I'm still running on the left pump only and will probably fill up tomorrow. If it starts playing up I'll test the pressure again immediately.
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I have always filled with Shell V-Power, but from different garages. I have a fuel pressure tester on order, but the problem feels intermittent. I generally drive the car very gently so would low fuel pressure cause problems at under 2,000 revs with light throttle opening? It feels like either the electrical supply to the pump has been interrupted, or the pump suddenly is sucking up air, or the plugs have stopped sparking. Would the fuel pump go weak intermittently?
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I drove a bit further today, about 15 miles in total since filling up, still running perfectly. So I pulled fuse 13 and refitted 14, and it still runs perfectly. Will carry on driving with just the left pump to see what happens
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Well I have been running with fuse 14 pulled since my last post and it's been running fine. I got down to about a quarter of a tank and filled up today, and it still runs fine. So it looks like a problem with the left pump. I will run it for another day or so to confirm., then pull fuse 13 and refit 14 to see what happens Long shot, but could it be the relay? I'm inclined to try swapping them as it's easier than a new pump. Can anyone tell me which ones they are?
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I found this on line With the activation of drivers outer door handle - left pump primes fuel rail. starting procedure: left and right pumps on Fuel tank qty >60 L right pump on full load: left and right pumps on. Fuel tank qty < 60 L left pump on. full load: left and right pumps on. If this is correct the right pump runs when the tank is full, I have pulled fuse 14 so the right pump is always running and at the moment it's running perfectly. It doesn't make any sense
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I drove about 5 miles this morning and it didn't miss but the idle was a little lumpy occasionally. I pulled fuse 14 and it seems smoother but I will have to drive a bit more. Interestingly I found a description of the exact same problem on another forum discussing fuel pump issues. Sadly the poster never said if he found a resolution https://rennlist.com/forums/porsche-cayenne-forum/590120-cayenne-s-stalling-problems-how-do-i-test-the-fuel-pump-2.html
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After a bit of research it seems the hose with the green cap is the feed for the air suspension.
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"I'm a bit confused by the codes and number of air temp sensors you're seeing. I thought there was a built in "intake air temp" sensor on the MAP sensor and one mounted in front of the radiator (ambient temp)" I'm a bit confused too, I think the two sensors near the air filters are MAF and air temperature, and the one in the centre is turbo boost and air temperature. But I could well be wrong....
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My leaving the tank side of the purge valve open proved nothing. The car still misfired, still no fault codes. I decided to have a bit more of a poke around under the bonnet. I removed and cleaned the contacts for the other two MAF/Intake Air Temp sensors. I also cleaned the contacts for the two other devices near the purge valve that looked like they were attached to vacuum/vent hoses. Not sure what they are? I then had a look at the intake pipework. The right hand (sitting in the car) flexible hose that connects to the Y piece at the front of the engine wasn't pushed fully home at either end. After loosening the clamps it looked like it had been that way since the car was built and there didn't look like there was any chance it had been leaking. I fitted it properly just in case. According to the history I have with the car the air filters were changed about 4,000 miles ago, I thought I would double check. The plastic torx pins on the right hand side air filter box were in the unlocked position, but again I can't see this would cause any issues. I then noticed the small bore hose with a green connector that connects to the right hand side cover wasn't attached. I tried to trace it and it runs across the front of the engine and then disappears low down near the left hand turbo. Anyone know what this hose does? Could this be the issue?
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Trickle charger theory is out the window. It said the battery was fully charged this morning but I am still getting an occasional misfire. No fault codes and I monitored the air intake temperature in real time whilst driving. It was giving expected readings with no glitches when the car misfired. My reader's real time monitoring only shows one air intake sensor. As an experiment I've pulled the pipe off the purge valve on the tank side to see how it will run on the way home. My thinking being if the purge valve opens it will just suck in fresh air, not neat petrol
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Now after having a better look from what I can see my turbo has three Intake Air Temperature Sensors, one directly on top of the Y pipe, and one either side in the intake tubing near the air filters. Are these all used, and if so which is which? My fault code stated sensor 2 had a problem. To clarify I only blocked off the purge valve hose AFTER the car started to misfire following filling the tank, maybe I should have tried blocking it prior to filling up.
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Correction, I cleaned the connector for the turbo boost sensor
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Hi, yes the voltage was 12.6v this morning first thing before starting and without the trickle charger connected. A bit of a development, when I got home I connected the fault reader and it had an error saying the evap valve connection was open circuit, as to be expected. This was VW option on my reader. I then cleared this and checked the generic OBDII errors and got a message I have never seen before saying that there was a manufacturer specific error logged and it prompted me to select the manufacturer. Even though my reader doesn't support Porsche, Porsche was listed. When I selected Porsche I got the 2 following errors P0098 Intake Air Temperature Sensor 2 Circuit High P1880 Please refer to vehicle service manual I checked the connector to the Intake Air Temp Sensor and the contacts looked tarnished, and the orange connector seal didn't look in great shape either. I cleaned the contacts and ended up removing the seal completely as it wasn't sitting correctly, and filled the gap with silicon grease. I also removed the sensor and was surprised to see fluid sitting inside the inlet pipework. From a quick google P1880 is something to do with the transmission, not sure what - can anyone enlighten me? Both codes cleared themselves. I am going a bit further tomorrow so have put the trickle charger on as a precaution