Since the problem gets worse as the car warms up, I'd think it was possible
that something electrical was breaking down as it got hot. Also, since
changing the fuel mixture didn't make a difference, it makes me think
'74 Triumph TR6 | '63 Triumph Herald | '70 MGBGT | '84 Mercedes 300D Diesel
----- Original Message -----
From: "Navarrette, Vance" <firstname.lastname@example.org>
To: "6 Pack list" <email@example.com>; "Triumph List"
Sent: Monday, July 09, 2007 12:12 PM
Subject: [6pack] Colicky TR6. Prize for correct diagnosis.
> 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
> 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!