There seems to be a slight misfire when idling>>but not noticable while driving. All new plug>>wires, rotor, cap, plugs.>>Could an adjustment to the idle mixture screws>>reduce the HC to passable levels?>
The idle screw(s) would more directly adjust CO by way of richening or> leaning the mixture at idle. Extreme leaning would cause lean misfire> and send HC skyrocketing. How's your spark timing? How's compression?> Cylinder leakdown?
I have not checked these yet, will let you know. Steady vacuum reading of 20 at idle.>
HC is high in both idle and driving test.>>How is this significant?>
It could point to slight valve seat leakage. In a simple textbook> situation, not considering all of the real world variables, a burned> exaust valve can cause exaust gas to be sucked in on the intake stroke.> This technically "richens" the mixture because it displaces some of> the available fresh air volume that would normally come through the> intake. Also it can cause a partial cylinder misfire, which would> account for higher than normal HC.>
If you had a vacuum leak at idle I would expect to see really low CO,> but CO looks pretty normal for that engine. Plus, if that were your> only problem the numbers would improve dramatically at cruise.
William R. Watt 2 April 2005 18:48:52 [ permanent link ]
"Martik" (martik@telus.net) writes:
I have not checked these yet, will let you know. Steady vacuum reading of 20 > at idle.
you mentioned misfire at idle. should show up as small fuxuations in needle on vacuum guage.
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