I have a similar problem on my car. Patrick and Graham both said that if you
blip the throttle, it will close properly, and stay closed, and I've found this,
too.
Graham suggested it might be related to carbs. But I believe the problem on my
car is actually due to a missing throttle return spring. This is on a UK spec
1500, with twin HS4s. The throttle return takes the form of 4 springs: one on
the accelerator peddle and two from the top of the throttle linkages to the
inlet manifold - these are all present and correct.
The fourth one is missing from a lot of cars I've seen, including mine - it
connects the bottom of the throttle linkage to one of several places depending
on the model - suspension turret on early 1500s, a bracket mounted on the lower
part of the exhaust manifold, near the downpipe, on late 1500s, and I can't
remember where it connects to on earlier cars. The only place I have seen this
fully described is in the Moss parts catalogue. The spring and linkage both
seem to be made from unobtainium. I've considered finding an appropriate spring
in a hardware store, and using a piece of bent coat hanger for the linkage, but
haven't got round to it yet.
Hope that helps. If you manage to resolve this, please report back!
Dean
------------
PS - I believe the manual specifies that the correct idle speed is 700-900rpm -
can't remember exactly, but 1100-1200 seems a little high. If this car idles
rough at 800, there might be another problem. Mine idles fine at 750 after I
blip the throttle.
Date: Fri, 11 Aug 2000 19:30:10 -0500
From: "BILL McDEVITT" <wmmk1@informatics.net>
Subject: Fw: Tech Question
Received this question from a fellow Spitfire owner and
since I never encountered this type problem I will need
some professional advise!!! If you know how to correct
this, please email me direct, so that I may forward your
solution to him. Thanks. Bill
> I don't think you have been fully tested yet. Let's see how good you are.
> My car, after warmup, will idle at 1500 rpm. Yeah, I know that's high,
and
> I'd like to get it consistently at around 1100-1200, but....
> So I drive it around and it warms up more and I'm sitting at a light and
> notice that now the idle is maybe between 800 and 1000 and it's a little
> rough, not giving me a comfortable feel. The light turns green, I go, I
> drive, I stop for another light and maybe it's back up to a 1500 idle
again!
> It keeps yo-yoing like that and I can't figure out what the problem is.
> The car has plenty of pep! So, do you need more info or do you know how I
can fix this?
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