I believe it's caused by the way dashpots work. Not necessarily the oil as I
use a 20 wt. in mine and have the slow return to idle as you do. No smog
stuff on mine at all.
Mike
'79B (SU HS4's)
----- Original Message -----
From: "Paul M." <rowman22001@yahoo.com>
To: <mgs@autox.team.net>
Sent: Wednesday, May 07, 2003 3:44 PM
Subject: "hanging" revs...
> 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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