Problem Finally Solved

1997 Volvo 960 77,000 Miles. For some time I have been suffering terrible fuel consumption - short runs about 12 mpg. I bought a diagnostic code reader which told me only problem was a faulty catalyst sensor. Car due for service and MOT so got garage to fit two new cat sensors during the service. However, car failed MOT on emissions- way too high. Garage full diagnostic equipment was used and it told mechanic only problem was the timing of fuel to the injectors was twice as long as it should be i.e. engine way over fuelled. Mechanice said this timing was primaraily controlled by main CPU. As it happened I had in the past bought a spare used ECU on Ebay as it was so cheap, so in it went - Problem solved. Emmissions now CO Limit max 0.30% Mine now 0.02 HC Limit Max 200 ppm Mine now 17 I post this because I find it unusal for a main CPU to go faulty - but I may be wrong.

Lucky you had a spare ECU! :) As you suggested, I think an ECU failure is quite rare - its usually bad electrical connections or aged wiring that cause problems (or water ingress). Maybe I should do the same and nab a spare ECU from eBay...

Yowza. That is a nice thousand-to-one sort of solution. Thanks for posting and perhaps this should be added to the FAQ.

That is exactly what my garage have diagnosed with my car using far to much fuel and causing high emissions. But the price of the new one seems very high. Any idea where to get a 2cnd hand one? Thanks, Andrew

if the ecu input signals are correct and an output one is not , then it would suggest an ECU BUT a very very rare occurance to be an ECU ...