[T3] Car Runs Great, but Why?
Keith Park
topnotch at nycap.rr.com
Wed Mar 2 16:46:25 PST 2011
Often, the pressure sensors are not really quite right on anymore as they
drift with age, and this can make up for that... OR the fuel pressure isn't
right, maybe your gauge is wrong, OR the head temp sensor is not tracking
properly anymore...
Some ideas anyway.
Keith
.Bingo! All performance problems disappeared!...EXCEPT that it was still
somewhat tricky to set the idle to make acceleration smooth. To see what
negative changes there would be, I unplugged the Temp Sensor at the Air
Distributor.
Then, double Bingo!... The car now feels like new. It idles regularly,
accelerates without any hesitation (no need to rev a little), and it now
starts right up on the first key turn. With the Cold Start Switch
unplugged
and un-hosed, it needed at least a few key turns to prime up the fuel
lines.
But not now. Don't understand that. I've finally, bravely, gone out on
the interstates and...well...it's just fine. No troubling fuel smells, or
fuel leaking from heater box clamps etc. And, the oil level is staying
right at its level...no fuel getting into it.
I asked about unplugging that Temp Sensor not too long ago and was told
that doing that makes the Control Box think the engine is cold, and that
this
would lead to higher fuel consumption. Can't check that because I don't
know previous MPG anyhow.
So, what explains this? Why would sensor plugged in make car perform
worse? This must be a clue to something. I tried two other
sensors...but they made it a little worse idling and hesitating etc than
the original
one.
No...I haven't yet tested sensors in hot oil to check ohms.
That temp sensor just leans out the fuel mixture. With it unplugged, it's
causing the system to be 10% more rich than normal. The normal reading (with
an ohm meter) is 300 ohms @68*F. This is specified in the Elfrink FI
manual. I believe as the air temp goes up, the resistance drops (like the
head
temp sensor). I don't know what the lower limit is though. Ray Greenwood
told me that he normally unplugged his during the summer (it gets damn hot
in
Texas in the summer), and would plug it back in, in the fall.This helped
drivability issues in very warm weather, and kept the system from running
lean. Another approach is to balast the head temp sensor (factor approved
mod), using a 200 ohm resistor in series (set up to plug into the
connection
for the head temp sensor to wiring harness).
Since it running pretty decent, why don't you drive it the 13 miles to the
mechanic, and see if he can reset the idle?
Bob 65 Notch S with sunroof and IRS (Krusty)
71 Notch (Krunchy)
64 T-34 Ghia (Wolfie)
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