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Re: [T3] Hey Guys I'm still Bogged Down Over here!



Chris wrote:
I know others out there have my same problem. 70 Auto, FI that 
seems to get "slug like" after sitting at a light after loaded run on 
the Hwy in AZ. Review the question to the list a couple of days
 ago about "acceleration hesitation" Help me please, I only seek perfection!



Well, what do you mean by loaded run ?  Do you mean hot, uphills,
high speed and/or lot of acceleration events. All of the above.
You are suffering from too hot too lean condition. Get a head
temp gage to be safe! This condition is the worst of both worlds
if it is actually too hot and lean. Bad JUJU!
This is my essay for you.

I have had this problem  before.
Our fuel injection has two controls : temperature and air vacume.
When the engine is cold  the temp sensors send a signal to 
the "brain" to lengthen injection spray time thus creating a more 
rich condition. In cold weather with the engine stopped for Hours
the injection can put as much or more gas in the engine as a 
choked carburator and when it warms up less than and fully open
choke carburator. Quite efficient don't you think? When the engine 
has warmed up to normal/average  temps and the atmospheric temps 
are between 55 to 80 (comfortable temps for cars) the fuel injection is 
working at typical midpoint/fuel to air ratio efficiency. When the engine's
air temps and driving conditions are the harshest then the engine may be 
a little above normal/average temps. As the heads and air temps get hotter 
the temp sensors send less of the more gas signal, for the engine this is 
interpreted as just less gas or lean. On newer cars with EFI the oxygen
sensor compensates for the lean/rich condition by further autotunning
the EFI. The system was made to work with a steady temp increased
by the thermostat and at the top end of the temps controlled by the fan,
so you would have an average operating temperature at midpoint all
of the time. If you did not have a thermostat and you lived in those frozen
states then the fuel injection will always see a cold engine and the
sensors would signal for lots of gas at all times. In moderate to hot
weather,
if the engine was missing tins, for example, the engine temps would be 
above average to too hot; the temp sensors would see a hot engine and signal
for less and less gas the hotter it got. Pinging and overheating would
increase
by this condition apon acceleration. Kind of going up a steep hill for a
long
run: heating , leaning , getting slower and slower and still pushing it.

The head temp sensor has more control over the air temp sensor in terms of 
increasing injector's squirt time (fractions of second), During hot/lean
condition 
the engine usually idles crappy even though in the morning when just
starting 
it idled rock solid. This is because the fuel to air ratio is too lean to
give
your engine proper tuning. In carburated systems the cars sends gas 
evenly in all temps ; too rich for cold, good at average temps and too
rich at warmer temps; depends at what temps you adjusted it, that
is another reason why EFI is more fuel efficient if everything is working.

If you beleive your engine is running too lean during hotter engine temps
do this; disconnect the air temp sensor (in idle) and see if the RPM is
increases.
If it does increase during idle and gets more stable, Run the car and 
see if it feels better . This simulates cold air and commands the "brain"
to feed a little more gas. 
Some people claim no effect when disconnecting this sensor. This probably
because it is faulty or at a particular temperature it is already a little 
at midpoint to a little richer and this being disconnected just sends
a little more gas the engine does not require but is not too much,
kind of having a fine mixture screw on a carb in addition to the 
coarse adjustment mixture screw (if they had both)
If engine seems to run better, then the engine 
was either roasting and about to die (doubt it) or you have an engine
head temp sensor that has changed its resistance, wrong head temp
sensor, or you need a replacement head temp sensor with different
resistance (got part numbers) or you need to fool the sensor by placing 
a washer under it (will simulate cooler temps and inject more gas) or  you
need to install ALL  cooling tins or you need to increase overall
mixture by tweeking the pressure sensor to a richer condition
 (by following the proceedure I sent to MAT this week ) or you have 
some weak injectors that show up only during hot conditions (the
less fuel engine hot command adds leanining to already lean injectors)

 or you 
can place a fuel ratio meter and fuel ratio adjustment (from head temp
sensor) on your dash. Your problem is temp vs fuel ratio. You can do
alot with these EFI's.  I have corrected this problem very nicely. It's
now smooth and fast. It is set a little on the richer side to keep the
engine cooler.

E-mail me if you have any questions.

LEON MARTINEZ
martinezl@ftscpac.navy.mil

1969 SQUAREBACK EFI/AUTO
SAN DIEGO AND TIJUANA



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