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

[Alexander Ishii (alexishii]

Hi Jeff,

> First, check all the spark plug extenders closely. You could have one
> starting to burn through, which could be causing your symptoms. Very common
> problem. 

I would have thought that my mechanics would have noticed this when they
changed the plugs, but then again, they don't seem to be able to notice a
suspect engine idle, so I guess a double check on my part may be in order...

> Next, check the carbon brushes inside the center of the distributor caps,
> I've seen these break and/or wear down and cause problems. These brushes are
> available as a separate part from the (expensive) distributor caps.

Will check this also, and let you know what I find.

> Make sure that the oxygen sensor is working properly too. Back probe at the
> single wire with the engine running and warm. You should see the voltage
> swinging between 0 and 1 volt, averaging at .5 volts. This is best done with
> an analog multi meter, or scope. A DMM may not show the voltage changing. If
> the voltage seems stuck (not changing) then it could be the oxygen sensor is
> dead. Low voltage below .5 volts would indicate a lean condition, higher
> above .5 volts would be rich.

Ditto here.

> If all this is ok, and you are 100% sure there are no vacuum leaks (the only
> reliable way to tell for sure is with the use of a smoke machine ...
> somewhere I have instructions on how to build one, if you or anyone else
> wants them, LMK and I'll see if I can dig them up. If you are not familiar
> with the use of a smoke machine, go here ... www.redlinedetection.com) the
> next thing to check are the fuel pressures.
> 
> CIS is VERY dependent on fuel pressure(s) and failed or gunked up control
> pressure regulator with cause havoc with the system. This requires a special
> fuel pressure gauge with a three way isolation valve that is connected
> between the fuel distributor and control pressure regulator.

Don't imagine I have one of those in my tool box... :)

> If the fuel pressures check out ok, then measure the duty cycle at the
> frequency valve. Several QV's have been having problems with the duty cycle
> at the frequency valve being incorrect. I have some PDF files that include a
> diagnostic flow chart for this convoluted system. LMK if you (or anyone else
> wants these files)

I'd be interested in the files.

> If the fuel injectors have not been replaced in the last 10 years, by all
> means replace them with the upgraded injectors. CIS injectors are famous for
> having poor spray patterns when they age. It may not solve this problem, but
> it will definitely help to maintain proper running and will be a step in the
> right direction.

Yup, it seems like a good "let's make sure it is not something really basic"
measure...

    Cheers,
    Alex

> -----Original Message-----
> From: Alexander Ishii [mailto:alexishii [at] mindspring.com]
> Sent: Thursday, December 23, 2010 1:01 PM
> To: Jeff Greenfield
> Cc: The FerrariList
> Subject: Re: [Ferrari] 308 QV emissions failure and possible misfire
> 
> 
> Hi Doug,
> 
>> Ahhh Alex - the ever wonderful world of CIS, the constant injection
> system.
>> VERY temperamental to air leaks.
> 
> Yup, I've looked over all the leak points that I can inspect without pulling
> the major plumbing bits, and found nothing that looked suspicious (or that
> had an effect on the idling when "wiggled").  My plan is to replace all the
> hoses when I take the thing apart, just for good measure.
> 
>> Especially at the boot area.  The pop you
>> hear may be a misfire fired off in the cat (shudder)
> 
> I also hope this is not the case.  I don't think it is, as the source of the
> "pop" seems to be close to the engine, rather than back where the cat is.
> 
>> but most likely it is a
>> lean mixture misfire spit back.
> 
> This certainly would mesh with the engine-temp issue.
> 
>> 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.
> 
> At idle the results are:
> 
> HC ppm  270     (pass is 220)
> CO%     0.51    (pass is 1.2)
> CO2%    14.6
> O2%     0.5
> 
> At high idle the results are:
> HC ppm  100     (pass is 220)
> CO%     0.52    (pass is 1.2)
> CO2%    14.5
> O2%     0.3
> 
> Any thoughts would be greatly appreciated.
> 
>      Cheers,
>      Alex
> 
>> ----- 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
>>> 
>>> 
>>> _________________________________________________________________
>>> To unsubscribe or modify your subscription options, please visit:
>>> http://lists.ferrarilist.com/mailman/options/ferrari/dnt%40dock.net
>>> 
>>> Sponsored by BooyahMedia.com
>>> and F1 Headlines
>>> http://www.F1Headlines.com/
>>> 
>> 
> 
> 
> _________________________________________________________________
> To unsubscribe or modify your subscription options, please visit:
> http://lists.ferrarilist.com/mailman/options/ferrari/coyote%40acme-ltd.com
> 
> Sponsored by BooyahMedia.com
> and F1 Headlines
> http://www.F1Headlines.com/
>