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

[Alexander Ishii (alexishii]

Hi Larry,

>     It's often the most simple of things that cause problems - look closely
> at all hoses - inspecting for looks connections, damaged hose ends (usually
> from heat), damaged gaskets or loose flanges of all sorts.

Have checked to the extent that I can without disassembly, and did not find
anything obvious.

>     BTW - Did the problem start after the plugs and wires were replaced?

No, the problem predates the plugs and wires.

> Does it do it more when cold?  Hot?  All the time?

I think all the time, but it is easier to be sure the problem is there when
the engine is hot, and idling at its "hot" rate.

    --  Alex

> -----Original Message-----
> From: Alexander Ishii
> Sent: Thursday, December 23, 2010 10:58 AM
> To: Larry Turner
> Cc: The FerrariList
> 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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