[Mgs] [MG-MGB] Rough Running

[PaulHunt73]

Some increase in idle would be normal as you are creating a vacuum leak and taking a significant load off the engine at idle, so it speeds up even though the mixture is weaker.  However if your mixture is currently very rich and that is causing the rough running, as seemed possible from the audio on those videos you posted, then the increase could well be partly due to compensating for the excessive richness from the carb.  I must say I was surprised it still ran at all with the servo port unplugged (although I've never tried it), I would have expected the vacuum leak to be so high that the engine couldn't possibly run, that's what happens if the Welch plug blows out of the end of the inlet manifold.  I think there is a restrictor in that port though, which perhaps make the difference.

As to what to try next, until you have eliminated an over-rich mixture as a cause given the above, I don't see how you can move on.  You need a Colortune to monitor what is happening inside the cylinders i.e. check you have combustion in all four cylinders as well as mixture strength.

PaulH.


----- Original Message ----- 


  I removed it at the manifold end as it was a lot easier to get to - plugged the port there. Car ran the same when started, however revs increased noticeably when I removed the
  plug while the car was running. Still ran roughly but not quite as badly and with increased vigor, it seemed to me.
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