'86 EFCS (ESA) advance prob.

I'm having some weird things happening on my Electronic Fuel/Spark
Control system on my 318. When the throttle body is at hot idle, a
ground is put on the carb switch and the EFCS module is supposed to
stop all vacuum advance...or at least the book says that! I'm getting
instances when the module is providing vacuum advance at idle, even
with a ground present on the switch lead. The module itself is seeing
ground on lead N3, violet, which goes to pin 7, conn. 1 of the EFCS
board on the air cleaner. Sometimes, I get advance, sometimes I
don't. The manual states that there should never be vacuum advance
whenever there's ground on pin 1-7 from the switch.

Anything I'm overlooking here, except a bad board? This is a CA car,
7° BTDC @ 630 RPM, not the 49 state version. Does engaging AC cause
the spark advance to come on, or is there another sensor in play here?
If I just pull the hose off the transducer on the air cleaner mounted
housing, I set the timing for 7°, and then...sometimes...I get a fast
idle indicating advanced timing, and then it'll drop off. Hmmmm!

 

The EFC board is drawing current (around 80 mA) from Pin 7, Conn 1
when grounded and showing +12 VDC when open, so there's current draw
there, but it's not stopping the vaccum advance at all. I haven't
opened up the case yet, but I would think that this would strictly an
electronic function and have nothing to do with the vacuum diaphragm.

Anyone?? Help, as I have to pass Californai SmogChek II next week and
this ain't gonna make it, UNLESS the diaphragm's feeder hose is
supposed to be DISconnected when checking basic timing, in which case
it'll pass fine. I already know it's cleaner than clean on the dyno,
so no problem at 15 and 25 MPH.

 

The best thing to do if you are still running a vacuum advance
distributor, is disable all the switching crap- and run a straight
vacuum advance line from manifold vacuum to the distributor. This will
give you full vacuum advance at idle, and at all part throttle driving
applications- and a lot more power and driveability. More importantly,
the extra advance will give you 2-3 more MPG.

That switching crap is only there so the car will pass emissions tests
at the factory. It actually really hurts the engine's performance.
Run a straight line to the vacuum advance, on at all times.

 

It appears that the EFCS WILL allow more advance at idle only when the
feedback circuit is operating open loop. Once the O² sensor's up to
temperature and generating a signal voltage, it cuts off the advance
at idle. I tried checking basic timing both ways...with open loop and
vac. transducer disconnected, and with hot engine/good O² sensor
signal voltage, and got the exact same results. So, if you get done
with a job and just want to set the basic timing, if you take the
vacuum off of the diaphragm on the EFC box, it'll give you the same
results as if you drove around to get the sensor hot and then set the
basic timing. You'd think they would've explained that in the manual!

Make progress every day...duh.

 

On 1 Sep 2006 16:47:48 -0700, "duty-honor-country" aka Charlie Nudo of
Drums, PA, who never even served in the military and who has had 17
Google Groups accounts banned as of yesterday and will have

....which is a Federal felony in all 50 states...

'Tard...these Chryslers haven't had distributor vacuum advance in
YEARS. I'm not going to clue you in as to where it is, since you're a
brainless moron whose life only consists of being a Usenet troll and
attempting to destroy newsgroups you have no business even being
in....as your plagierized comments about the supposedly non-existant
1955 270 HEMI would suggest.

Suffice it to say that a simple diagnostic check of in and output
signals to the EFCS showed me how this feature worked. My '77 Honda
CVCC also supplies non-ported vacuum advance during warm-up through
the "Thermosensor A" thermoswitch.