CycleSi Posted June 8, 2022 Share Posted June 8, 2022 Got a 2002 1.8 R300K Superlight (but Ratrace Motorsport rebuilt and tuned to R500 232bhp spec) with Roller Barrels (balanced & optimised) and a MBE 967 ECU. The idle has always been a little erratic and less than smooth. Whilst playing around with it today I discovered if I disconnect the plug from the intake air temp sensor which is in the roller barrels back plate, the engine immediately smooths out and maintains a rock solid idle speed. Plugging it back in makes it run noticeably less smoothly. My questions are:1) Can I leave it permanently disconnected and/or will it do any harm.2) Should I simply replace the sensor with a new one?TIA, Si Link to comment Share on other sites More sharing options...
Amos91 Posted June 8, 2022 Share Posted June 8, 2022 Best plug it into Easimap and see what it's reading. It could be duff and affecting the fueling.Equally on my Sigma with it disconnected, it goes to a default and adjusts the fueling for a colder than an ambient temp at this time of year, so best to have it working. Link to comment Share on other sites More sharing options...
David_Long Posted June 8, 2022 Share Posted June 8, 2022 The MAP sensors do fail but seldom cause serious problems as they are simply fine tuning the map settings. The problem is that they tend to give erratic readings to the ECU when faulty. Unplugging it will set the default value that's a 'constant' value and may give smoother results. Either disconnect it (and accept that some conditions may be less than optimum), or get a new one. Link to comment Share on other sites More sharing options...
CycleSi Posted June 9, 2022 Author Share Posted June 9, 2022 Thanks Amos and David - that all makes perfect sense to me.I have ordered a new sensor and will fit that; but if it still idles better without it connected then I'll run it that way. I'll let you know my findings accordingly. Link to comment Share on other sites More sharing options...
CycleSi Posted June 13, 2022 Author Share Posted June 13, 2022 @ David - I have now fitted a new sensor and it is noticeably better, but it still has a much smoother idle when disconnected so I'm tempted to leave it disconnected.I guess my concern is will it do the AFR any harm in terms of running lean? You said it only 'fine tuned' the map settings so I'm thinking it shouldn't have much of a detrimental effect, but please correct/educate me if I'm wrong.Many thanks, Si Link to comment Share on other sites More sharing options...
Amos91 Posted June 13, 2022 Share Posted June 13, 2022 Sure the impact is minor but it will depend on what the actual intake temps are.With my air temp sensor disconnected (Sigma car), the Easimap software defaults to 11°C and shows a fuel trim alteration. Link to comment Share on other sites More sharing options...
Rob D. Posted June 14, 2022 Share Posted June 14, 2022 Hi Si,Has your car always had that state of tune or is this a recent upgrade ? RegardsRob. Link to comment Share on other sites More sharing options...
CycleSi Posted June 14, 2022 Author Share Posted June 14, 2022 It has been at this tuned level since 2018 so it is not recent. Link to comment Share on other sites More sharing options...
CycleSi Posted June 15, 2022 Author Share Posted June 15, 2022 Been out for a 100 miles or so this morning and it is definitely smoother/better left disconnected, so unless anyone tells me otherwise that is how I will leave it. Thanks for your input chaps. Link to comment Share on other sites More sharing options...
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