In a message dated 7/9/2007 1:14:23 PM Eastern Daylight Time,
vance.navarrette@intel.com writes:
Listers:
Just thought I would share my recent frustrations fixing a low
speed miss.
Since I brought the 6 out of storage, it has been very colicky.
At first I thought perhaps bad gas, then I thought it was just bitter
about not being driven all winter. Hey, don't laugh, I am sure you would
all swear your TR6 has its moods.
The symptom was a low speed miss when pulling away from a stop.
Sometimes it would miss once, sometimes it would miss twice, sometimes
no miss. This is not a bog, but a soft pop and the car will jerk
sharply. Adjusting the choke made no difference, and the problem would
occur when both warm or cold, although the problem got somewhat worse as
the car warmed up. The engine would rev just fine with no breakup or
missing at the upper RPMS. Battery voltage was about 14 volts,
temperature in the middle of the gauge, healthy oil pressure. Stock
ignition (Lucas coil and points, no Pertronix). No blue smoke, no white
smoke at idle or any other time.
My TR6 has a 270 degree cam, 9.6:1 CR, stock exhaust, dual
zeniths with B1AR needles. Carbs have been rebuilt, compression in all 6
cylinders is 145PSI +/- 5 PSI. K&N air cleaners in a stock filter
housing. Manifold heat is connected. 1974-1/2 car with EGR and all
emissions systems connected. Stock rockers, valve lash set at 0.015",
idle at 900 RPM - with what sounds like a very *slight* miss at idle. <-
another clue!!
OK, those are the symptoms. Here are some additional clues so
that you hairy chested LBC drivers can test your diagnostic acumen. I
say this because I always love a challenge, and I might as well torment
you all in the name of camaraderie. =:-o
Here are some additional clues:
1. Fresh plugs made no difference (Champion 12NY).
2. Adjusting the mixture rich or lean made no difference.
3. Fresh gas made no difference.
4. New plug wires made no difference.
5. Checked the timing, spot on at 4 ATDC dynamic. No observable
spark scatter when revved.
6. Wider or narrower plug gaps made no difference (+/- 0.005").
7. Vacuum retard functioning correctly.
8. Topped off the dashpots with penrite oil, still no
difference.
OK, listers. Do you think you know what I missed? Can you offer
a shrewd insight (or a least a derogatory comment) as to my utter
failure as an LBC mechanic? I know the answer, as the miss was resolved
just this weekend.
I am offering a prize for the correct diagnosis. The winner will
receive one "attaboy", redeemable with $2.00 for a cup of Starbucks
coffee and the glory of having his or her kung fu publicly acknowledged
as the best.
Post your guess to the list, Kastner wannabes!
Vance
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Vance,
Symptoms suggest a burnt intake valve(s).
Regards,
Vic Snively
'75 TR6 w/AC
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