Ferrari Mailing List: Re: 308 QV emissions failure and possible misfire

[Doug and Terri Anderson (dnt]

Ahhh Alex - the ever wonderful world of CIS, the constant injection system. 
VERY temperamental to air leaks.  Especially at the boot area.  The pop you 
hear may be a misfire fired off in the cat (shudder) but most likely it is a 
lean mixture misfire spit back.

Do you have a method to check CO?  These systems are set on fuel pressure 
and CO.

What is failing on your smog report?  HC, CO, NOx (do you test for that? 
Needs a dyne to do it or the test equipment is shoved in your passenger seat 
and your car is driven about - yes, they had that at one time)

Get me your readings - its like the engines blood test.

Onward
DOUG
----- Original Message ----- 
From: "Alexander Ishii" <alexishii [at] mindspring.com>
To: "DOUG" <dnt [at] dock.net>
Cc: "The FerrariList" <ferrari [at] ferrarilist.com>
Sent: Thursday, December 23, 2010 7:58 AM
Subject: [Ferrari] 308 QV emissions failure and possible misfire


> Hi All,
>
> So my 84 QV has been stubbornly failing emissions (in NJ), and after some
> repeated assertions by my usual mechanic that "all seems to be well", I've
> found myself having to try and figure out the problem myself.
>
> At the moment, the car is not idling right in my mind (despite what my
> mechanic says).  For one, the idle speeds "hunts" a bit; not enough to be
> seen on the tach, but enough to be felt as a slight change in the 
> vibration
> frequency of the engine.  Second, every couple of seconds one gets a
> just-audible muffled "pop" sound from the engine, accompanied by a slight
> puff of extra exhaust out of the tail pipes (no sound out of the air 
> intake
> system).  Also, the car is running sort of on the hot side (coolant temp
> "idles" at 195).
>
> Plugs and wires were changed not long ago, but other than that, nothing 
> much
> has required much tinkering in many years.
>
> The "pop" has me thinking than one-or-more of the cylinders is
> intermittently misfiring and dumping some un-burnt fuel into the exhaust
> manifold (where it is igniting and "popping").  Given the "every couple of
> seconds" nature of the problem, however, I have little doubt that all the
> sparks will look fine when I try the usual tests.  Anyone have any
> suggestions for how I might try and zero-in on the faulty system (short of
> swapping-out every part one-by-one until the issue goes away)?
>
> Also, it has also occurred to me that the problem might be that the
> injectors are not atomizing properly, and leading to an complete burn (in
> turn leading to exhaust manifold ignition of the leftover fuel).  Has 
> anyone
> seen symptoms like the above be remedied with replacement of the 
> injectors?
>
> All thoughts/opinions/experiences would be appreciatively accepted.
>
>    Cheers,
>    Alex
>
>
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