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Any ideas on how to cure this please. M42 engine, which came from an E36 coupe. To get round the EWS, an E30 ECU is used. When it went for MOT, the CO was too high. After cleaning bits, and replacing plugs, the CO at higher revs is OK, but at tickover its still showing 6 %, where a pass needs 4.5. None of the sensors seem to be giving odd readings, Im told. The garage is thinking the ECU may be at fault, and want to send that away for checking.
Any ideas would be most welcome !
Neil

What sensors were checked? No expert on the M42, not at all, but it is likely to have temp sensors for both coolant and intake air that can be at fault, but most likely the 02 sensor (if any is fitted) is at fault. Disconnect or have it programmed to 'off' in the ecu (I know that was an option in the good old MoDiC but I don't have one anymore).

Thanks, Jeroen. I dont know what sensors they tested. Dont think there is a intake air temp sensor. Because the coolant sensor runs to the ECU, I had to put an extra temp sensor in for the temp guage, and that confused things too. My extremely limited knowledge pointed towards the O2 sensor too. Hopefully more news in a few days
Neil

It appears that E30 and E36 M42 engines use different injectors, and Ive got a later engine with early ECU. Early injectors fitted and it passes emissions.

The devil is in those details... Glad you found a solution.