wall street Posted July 2, 2007 Share Posted July 2, 2007 Hi My 3.9 hot wire efi is suffering from excessive over fuelling. The plugs are jet black after only 50 miles or so. I have changed the ECU temperature sensor and fitted a new air filter. Any other ideas? What should I be looking at checking / replacing next Thanks in advance. Rgds John. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted July 2, 2007 Share Posted July 2, 2007 Is the fuel pressure relief valve / pressure regulator working? There is an air temp sensor in the airflow meter, also if the airflow meter is knackered that would do it. If there is an air bypass on the AFM (like flapper) try opening it up to lean it out. Do you have lambda sensors, if so are they working? Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted July 4, 2007 Share Posted July 4, 2007 The HW 3.9 AFM is often guilty here. When it fails the unit will go to Max air and Max fuel settings...... Try disconnecting the AFM Plug see if it is any worse, if not then suspect the AFM, if it gets even worse then its not and reconnect it ! Nige Quote Link to comment Share on other sites More sharing options...
V8 Freak Posted July 4, 2007 Share Posted July 4, 2007 I read somewhere that your require a 470ohm resistor in there somewhere if you are not running Lambdas.... Mine was running rich and sooted the plugs after a while... Resistor was duff... Fitted new resistor which effectively told the system there were not Lambda's and all working fine now... Might also be worth checking advance / retard mechanism.. Mine was dead (Diaphram holed) which meant I wasn't getting the best burn in the cylinder.... Neil Quote Link to comment Share on other sites More sharing options...
wall street Posted July 13, 2007 Author Share Posted July 13, 2007 Many thanks all AFM; typical. Quote Link to comment Share on other sites More sharing options...
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