Pete Underhill Posted August 16, 2014 Share Posted August 16, 2014 On my standard factory setup on a Sigma 125, when blipping the throttle on the downchange, instead of the rev increase, I get a 'PSHHT' sound, like a cat sneezing. Then, by the time the engine responds, it's too late and the gear change has been made. It behaves the same at all temperatures, even after twenty or so laps of Bruntingthorpe. On normal progressive throttle use, it feels fine. Can the community offer any thoughts? Link to comment Share on other sites More sharing options...
DJ. Posted August 16, 2014 Share Posted August 16, 2014 I have a standard Sigma 125, and it blips very quickly on down changes, hot or cold. Sorry I don't have any real idea what's causing your problem, but it isn't right! I suppose you could look for a manifold leak? Duncan Link to comment Share on other sites More sharing options...
Pete Underhill Posted August 16, 2014 Author Share Posted August 16, 2014 It was blipping very nicely until Wednesday. Link to comment Share on other sites More sharing options...
revilla Posted August 16, 2014 Share Posted August 16, 2014 Throttle position sensor? Check the connector is secure and wires intact. I think the TPS normally gives the ECU a "heads up" on a blip allowing it to repond immediately, before pressure and flow signals stabilise. Link to comment Share on other sites More sharing options...
AndyD Posted August 16, 2014 Share Posted August 16, 2014 Check the little black rubber tube that plugs into the thing next to the ECU. No idea what it's called so could be what he said . Think it's used on the 125 but disconnected on the 150 (hope so anyway, as my 150 has no pipe plugged into that thing). Link to comment Share on other sites More sharing options...
ChrisC Posted August 16, 2014 Share Posted August 16, 2014 Its called the map sensor. Its electrical connected on the 150, but the 125 uses it to sense manifold pressure. Its possible you have a split hose between the manifold and the map sensor. Link to comment Share on other sites More sharing options...
AndyD Posted August 17, 2014 Share Posted August 17, 2014 Exactly Link to comment Share on other sites More sharing options...
Pete Underhill Posted August 17, 2014 Author Share Posted August 17, 2014 Thanks for the pointers. Once the weather settles down, I'll get out there and take a look. Cheers Link to comment Share on other sites More sharing options...
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