Re: SIII Rough Idle (Different problem)

[Randy Wilson <randy@taylor.infi.net>]

>
>
>1984 4.2L Fuel Injected:
>
>A couple of questions about idling:
>
>1.  Is recommended idle speed set in neutral or while in 'D'?
>2.  How much drop in idle should take place between neutral and 'D'?

I like to see 800 in N, with it only dropping to 700-725 in gear.


>3.  Should there be a "fast" idle when cold? (Mine's 600rpm always, when in
>D

Yes, but it's nothing like a carb fast idle. Depending on ambient conditions,
maybe 900-1000 stone cold.

>4.  My idle is FAR smoother when engine is cold.  At normal op temp the
>engine appears to mis-fire intermittantly. What sensor(s) could it be? 
>What else should I check? (Has new rotor, cap, wires, coil, plugs).


Vacuum leaks. Injector seals, vacuum hoses (and cap) under the manifold,
the hoses to and from the aux. air regulator (your fast idle device), the
plumbing from the air flow meter to the manifold.
Leaking manifold gaskets on the XK engine are rare. Much more common on the 
V-12 and AJ6.


>5.  A click can be heard in the engine bay at idle, roughly every 30
>seconds which coinsides with a slight increase in rpm.  What is this and is
>it key to my problem?

Most likely the A/C compressor cycling.



   Randy K. Wilson
     randy@taylor.infi.net

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References:

• SIII Rough Idle (Different problem)
• From: "Andrew Sandiforth" <acer@serv.net>

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