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Date: Mon, 23 Nov 1998 20:13:37 +0100
From: johnnopsam16.co.uk (John)
Subject: Re: should cold idle be the same as warm idle


Dear Jerry, In a word yes, the Idle should remain constant whatever the temp . An engine requires a certain amount of fuel and air to idle smoothly when warm if this same ratio / quantity is supplied when cold the engine would run rough, idle at a much lower speed and even stall this is because the fuel cannot vapourise propperly at low temps and does not burn properly/efficiently - it needs more fuel - increased pressure on mechanical fuel injection or increased injector opening time (twice per engine rotation) on the electronic fuel injection systems. You also need more air to keep the idle up but it does not have to be so much that the engine has to run faster than normal. Most engine wear occurs in the first few seconds of a cold start before the oil has a chance to flow around the engine (especialy if you don,t have a non return valve in your oil filter - some cheapo ones don't) - you do not want the engine racing up to 1200 - 1500 rpm at this time - something you can do with carb engines with a manual choke. I have had 3 900,s all, when I have set them up properly, have idled at about 850 rpm in any temp. Hope this helps John

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