4KQ Smog Problems-Update, still stumped

[urq]

... 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)

> Ok, I am really stumped on this one, remember, this car is at 1900ppm in
the
> HC, Gross Poluter is 240- here is what I have done/checked to date:
>
> -Plugs/wires/cap/rotor
> -Swap ign. distributor with one known to be working
> -Compression Check, 150 across all cylinders
> -Pulled injectors, look almost new, soft/pliable seals still on, perfect
> spray patterns at all elevations of plunger
> -Timing at 6BTDC
> -Crank, cam, dist all in alignment
> -CO set at 10mA and it fluctuates between 8 and 11mA
> -New O2 sensor, visual inspection of cat
> -Water temp sensor changed with known working one
> -Throttle switches tested and working.
> -All vacuum lines changed, no vacuum leaks
> -Vacuum advance canister NOT working, but plugged with RTV to prevent
leak.
>
> The car is very driveable, accelerates well, frankly if it wasn't for the
> smog numbers its a great running car.  It does have a slight miss, though,
> and I think this is at the root of the problem.
>
> Interesting to note, when I pull one plug wire at idle there is hardly any
> change in the idle, and the engine accelerates well with the throttle
> blipped, and it does this regardless of which plug wire is pulled, almost
as
> if this miss moves between cylinders.  I am becoming convinced that its an
> electrical problem, not a fuel problem, the only thing I have not changed
in
> the ignition system is the ECU and the Coil...I have a working ECU, maybe
I
> will swap it and test that.  Any idea what could cause such a good running
> car to fail the HC test by a factor of almost 20??
>
> TIA,
> Javad
>
>
>