hi,

1998 disco 1 v8i ES , always run lumpy, sounds like 7 cylinders when cold or under load. plugs are all same colour - white/light brown.

I have a ecumate and it shows..
- all sensors working, eg water temp fuel temp, tps,idle stepper..
- MAF is only 1.4 volts at idle, some docs say it should be 1.8 volts..but it goes up when revved.
- white tune resister +cats - matches what i found in the wiring.
- The really odd bit is the lamdba oxygen sensor values..

lamdba sensor a ( nearside bank) oscillates around +- 10 , on the overrun it says lean , foot down it says rich - looks good.
lamdba sensor b ( offside bank) - oscillates wildly +-100s , but again sort of follows the mixture.

with the different behaviour I changed the two sensors for 2 new ones and they stayed exactly the same...

So yesterday i bit the bullet and got the multimeter out.

- unplugging sensor a - both sensor values stop changing - no fault logged though!
- unplug sensor b - no change at all!!! both sensor values carry on exactly as before.
- disconnect ECU ( date code 1098) , sensor b signal goes to ecu pin 24 , sensor b ground is ground, sensor b 12 volt is 12 volts.. no shorts of x-connections all looks good.
- i should have done sensor a at the same time and checked for any x-connection but that's a job for today.

So having looked at the the rave circuit diagrams and the above experiments it looks to me like lambda b is getting lambda a's signal plus some other rubbish probably inside the ECU as the wiring loom for sensor b checked out ok.

Sound sensible? is there a recommended ECU tester/repairer?
thanks
tim