Paul:
When you slam the throttles closed, the mixture in the engine goes
imediately rich until the unburnt fuel in the intake tract is used up.
This is an emmision no-no.
The system is designed to over-run slightly to allow the fuel to burn out,
that's what the gulp valve does. In fact in some instances the air injected
into the manifold under high vacuum conditions will cause the engine to go
lean, increase in speed and give a few backfires.
Disconnecting the small vacuum sense line to the gulp valve will defeat this
system. But, as you say "if it aint' broke".
Kelvin.
> Many thanks to all for helping with my "heel ond toe"
> quandry. I think I'm well on my way to having it
> licked, with everyone's great advice and help.
>
> Moving forward (remember that I've only owned this car
> five days, so expect the questions to keep coming in a
> flurry for a short while yet...), I have an issue with
> the way the engine responds off throttle that I find
> perplexing.
>
> This car is a 1971 tourer, and the engine compartment
> is remarkably unmolsted. All of the factory emissions
> equipment is in place and working well. It fires
> right up, idles great, and runs smooth and docile.
> But it does something that I find strange:
>
> If I'm at idle, and I blip the throttle, the engine
> responds quickly and revs freely, but when I lift off
> the pedal, the revs kinda "hang" up there and come
> back down to idle somewhat slowly. Not REAL slowly,
> but just a little slowly... Is this a function of the
> air pump or something? My old B was a 1963, and it
> didn't do this at all. One thought is that it could
> be the simple fact that it's a 5-main engine and I'm
> used to the more responsive 3-main. Another thought
> is that it's the air pump and related emissions
> controls stuff, and "desmogging" it might help
> (although I am loathe to do that, since it's running
> so nice and since I would feel bad about yanking
> everything off a good original engine), and a third
> thought I had is that the dashpot oil might be too
> thick or something (in which case a recommendation on
> what to use would be wonderful...)
>
> Any thoughts? Do all later B's do this?
>
> Thanks again,
> Paul
> 1971 MGB Tourer
> (Still searching for a nickname, but leaning towards
> "The Pumpkin", since it's blaze...)
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