rasheed

Well-Known Member
Hello, have a question about tuning my 4.0 V8. She has cats but no O2 sensors! They're not missing, they were never fitted. No plugged holes in the pipes and no loom to the ECU. So can anyone tell me what the ECU uses to decide the mix and timing and what are the "learning trims" that apparently can be reset to default with diagnostics?

Basically I'd like to very slightly advance the timing and also make the mixture a teensy bit leaner. Any advice on how to do this would be highly appreciated!

Cheers!
 

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