'7747 & two A.I.R. valves - CrossFire retrofit

[rr]

Have some info here. This is according to a '92 Camaro TBI system
running the '8746. Same hardware, different code than the '747.
This area is most likely the same.

The port solenoid (EAS, pin C2) controls air to the manifold.
The divert solenoid (EAC, pin C1) controls air to the cat-con.

On the '747, the PSPS does nothing. Neither does the A/C out.
However, the A/C in (pin B8) is so the ecm knows when the
A/C compressor is engaged & bumps the idle up. Wire it to
the compressor clutch.

There is no ccp function on the '747. However, there is a cold
start kick soleniod function that may work for the ccp. It has
three parameters: two temperature quals & a tps qual. Might
be able to play with the values & get it to work.

Heres something interesting: on the '8746 the PSPS is used
during idle & high P/S loads. It causes the ecm to bump up
the IAC and retard the timing a little. Helps prevent stalling.

BobR.


Ken Kelly wrote:

> Duh. Kinda answered my own question, sorta. I jumped on CarParts.com and
> selected different vehicles that I knew used the '7747, and looked in the
> AIR/CAT replacement part section to see if the two valves were listed.
> (Yikes.. they're almost $200 each!) The '88 C1500/350/VIN"K" Suburban
> apparently had both valves. Going over to Ludis' C3 crossreference, there's
> over a dozen calibrations just for the "K" VIN.
>
> I just looked at the two 1227747's I have that I yanked at the junkyard;
> they are both listed (externally, on the box) as AKAJ, yet one of them has
> an AMUR PROM in it (the other one actually has the AKAJ PROM in it.) They
> both came from 1988-1990-ish Suburbans, 350 TBI. (I can't remember what
> year, and I kick myself now for not noting it!) Apparently the '88 Sub used
> two valves, one being the AIR control valve, and the other being the AIR
> "diverter" valve. The '89, '90, and '91 Subs used an AIR control valve and
> an AIR "bypass" valve. (Which is which??)
>
> The CrossFire schematic for the emissions shows an AIR "control" valve which
> is the main valve off the pump - it switches between the air cleaner or the
> second valve, called the AIR "switching" valve - which I'm assuming is
> probably going to be the "bypass" or "diverter" valve equivalent. (y/n?)
>
> Also, Cannister Purge Solenoid is apparently used only on '90-'91 Subs.. so
> I need a '90-'91 Suburban PROM to start with.. any ideas?
>
> Ken
>
> ----------------------------------------------------------------------------

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