Engine Problem when Hot - Fixed!

From: Ian Powis
email: ian.powis@ehotspot.co.uk
Date: 21 Oct 2006
Time: 10:12

Message

I'm pleased to say that I've fixed the engine problem I've had for the last few weeks, and thanks to everyone for the advice and suggestions. I have to own up though and say that the problem all along was the injection system water temperature sensor. I changed this today and bingo - engine running smoothly again, so took it for a long run just to make sure and got an acknowledging flash and wave from a Maserati Quattroporte! As suggested I did have a look at the fuel tank, and took this out but it looked very clean inside. At least this gave me the chance to replace all the hoses. The fuel delivery through the hose to the cold start valve test as previously described by Peter Still showed 3 litres/minute and the injection manual says 1.5 - 2.0 litres so I thought this was fine - in fact I was worried it might be too high. Anyway, after checking the fuel system the problem was still apparent. It felt like there was too much fuel, just like the the choke being left out on a carburettor car. I checked the thermo time switch and the cold start valve and these were OK. I'd previously checked the resistance of the temperature sensor at the ecu plug as per the manual and found that although it wasn't spot on it was close. So I now suspected a faulty fuel pressure regulator but thought I'd just check the temperature sensor again by checking the resistance. It was 112,000 Ohms instead of the 3,000 it was supposed to be. I swapped the sensor and the resistance showed as around the 3,000 Ohm level. I started up and the difference was immediately noticable and the car now runs smoothly. My theory now is that the sensor must have been failing intermittently for a time, and when I last checked, it had reset, maybe even the failure was temperature related and it got worse as the engine heated, but eventually it gave up altogether. My local auto parts shop even had a new one in stock. It's not a Bosch original but is from a company called Facet who are Italian. On the box it is listed as for the Alfa 75 and 90 2.5i V6 part number is N55460 and manufacturing date on the box is 26/01/05 which is encouraging. Attached you can also see a photo of the strut failure that caused our trip to Turin to end ignominiously even before we'd got to Dover. It's embarassing to show the state of it, because it's so rusty. The combined additional weight of my emergency spares box and the luggage obviously did for it. Having previously been of the attitude "if it ain't broke don't fix it" I have rapidly changed my views and will make sure I have a good look at the rest of the suspension over the winter. Thanks again to everyone for your assistance.