Posted: Sat Jan 06, 2007 12:53 am
Maybe if Phil sees this he can explain what the MS extra software does with advance retard. MS only sees full vac via the map sensor so it would be interesting how they worked it out.
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One side effect of retarding the ignition is that it produces less power (and more heat) so you need more throttle, so you get higher gas speeds, less manifold depression, less EGR and better air/fuel distribution. These effects could conceivably be contributing to your misfire at idle.Paul B wrote:I thought it clarified a useful bit of much-misunderstood information, but I'm now not too sure about using manifold vacuum in all circumstances as it appears to have been the cause of the erratic misfire at idle that has plagued me for a year or so. I'm pretty sure it has gone away every time I've disconnected the vac advance.GreenV8S wrote:That's the one, well worth reading.Paul B wrote: Is this the one by perchance
Even after fitting a different dizzy and a brand new carb and manifold system it was still there, but removing the vac advance 'appears' to have cured it. I now run it on timed/ported vacuum and it seems smooth as silk.
I've not had it like this for many miles so it could be (yet) another wrong lead.
So maybe I've merely 'masked' some other problem by changing my vacuum connection to the timed port, such as worn valves guides, sticky lifter, cracked valve seat etc?GreenV8S wrote:
One side effect of retarding the ignition is that it produces less power (and more heat) so you need more throttle, so you get higher gas speeds, less manifold depression, less EGR and better air/fuel distribution. These effects could conceivably be contributing to your misfire at idle.