4KQ Smog Problems-Update, still stumped

[JShadzi at aol.com]

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Hey Steve, I have basically changed everything in the car except the cat,
which I will do this week, hopefully that will be it, or at least mask the
problem.  I want to reiterate that the miss is so tiny that its almost
imperceptible, the 5 cyl is not the smoothest running motor, it might not
really even have a miss.  The emission numbers look as though there is no cat
in place, so that is the next step, even the cat looks fine, I have seen them
not fire.  I'll keep you all posted,
Javad


>
> ... since I [kinda still ... unfortunately ...] have an '85 4kQ and live in
> California I can provide a data point that a car with a dead vacuum advance
> can pass smog ... my car does this quite handily.  Frankly, I wonder how
> many cars have a functional VA.  BTW, if you need a replacement vacuum motor
> I do have one in the garage that I want to install ... you're free to borrow
> it to see if it does the trick.
>
> I was in a similar boat on the urq, but in that case there was low comp on
> #2 and I was able to smog the car easily once I got a head with a good set
> of valves.  The car would do OK on the high rev test, but when I went to
> idle the HC would start out OK for a while, but then creep up slowly to GP
> levels ...
>
> Remember that on this car the ECU only controls mixture ... via the EHA on
> the the airflow sensor/filter box... spark is not that different from the
> old points days with a Hall Sender replacing the pints and an electronic
> module driving the coil.
>
> I think that the "slight miss at idle" that you report is in fact the cause
> of the high emissions ... a single miss dumps raw gas into the exhaust.  I'd
> expect that normally the cat would take care of most of this ... is the cat
> functional?
>
> I would tend to agree with your suspicion that the issue is not fuel related
> ... so there is no need to think about the ECU.  There are only 3 parts that
> you have to test ... the Hall Sender, the coil driver and the coil itself.
> I'd also recommend setting the timing to stock ... don't try to fake out the
> dead VA.  It might even be good to simply swap the dizzy from another car if
> at all possible ...
>
> Good luck Javad!  You're welcome to drop by if you think I might be able to
> help you out!
>
> Steve Buchholz
> San Jose, CA (USA)
>