After playing around with different ECUs on my XJ12 HE 1983 (emissions B: europe – no cats, no lamda, no O2 sensors), I finally decided which to use in the future. Unluckily, this ECU (a 16CU) didn’t come with the car, so I thought it would be a good idea to calibrate the ECU using the built-in potentiometer and a CO measurment device (my choice: Gunson’s Gastester G4125). It turned out that the ECU was set a little too rich (4% CO), but turning the pot a few clicks counterclockwise did the job.
So far, so good. However, I noticed an interesting difference between the two banks regarding the CO readings. After the calibration (I aimed at 2% CO – get rich or die tryin’, eh?), the right bank provided a reading of 2,3% CO, with 1,9% CO on the left bank.
Is that an acceptable variance, or something to worry about? I was thinking: Could the location of the idle adjustment screw on the left intake manifold result in the left bank running slightly leaner than the right bank? I know that the left and the right intake manifolds are connected to each other, but even air may like to take short cuts??
I should add that there was a problem with an injector on the right bank, which lead to cylinder A4 running terribly rich. That is now solved since a few hundred kilometres. I also used some additive to clean the system (valves and injectors – at least, that’s what the ads claimed), but, of course, it could be that A4 is still a little more carbonized than the other cylinders.
Everythin else has been double and triple checked (and in many cases: repaired) during the last weeks for different reasons, all of them being more or less related to a careless PO: throttle plates, injectors, injector hoses, injector wiring, spark plugs, distributor, ignition timing … It really took some effort, but now the car runs perfectly smooth under all conditions, the same applies to the idling.
So, what do you think? Should I just leave it that way, or dig into the ignition system – again?