Hi Folks,
Ken Streeter wrote:
>I have received many responses regarding my TR6 which is missing
>occasionally at speed on the highway. I figured I'd give the whole
>list an update, including some information from Bob Lang that may be
>of interest to others. I want also to thank all respondents, which
>have included Colin Brace, Adrian Jeffries, John Lye, Doug Phillips,
>Marcus Tooze, Randy Wilson, and David Yip. This response is pretty
>long, but has a number of questions buried within. Any and all
>comments and suggestions are welcome, as long as nobody suggests
>using epoxy to repair my brake lines... :-)
[stuff deleted]
>I may have made some more progress on the missing at speed
>problem. Unfortunately, I haven't driven the car under the same
>circumstances as were showing the problem to see if it has been
>fixed. (We have had about 4 consecutive days of on/off drizzle
>keeping me from driving the TR6 to work, and a forecast for about 4
>more such days... :-()
Hey, I drove my TR6 in the rain last weekend! It worked okay. Of course
I had to put the top up ;-).
>Despite last weeks rain, I was closely examining the workings of the
>carbs and the throttle linkage to find out what parts are missing
[stuff condensed...]
>It turns out that the spindle coupling between the throttle shafts
>of the carbs has play in one direction. What I mean is that if one
>turns the throttle spindle for the rear carb manually, the throttle
>spindle for the front carb moves too, with no play. However, if one
>turns the throttle spindle for the front carb, the spindle coupling
>in the middle slips for about 30 degrees, and then starts to turn
>the rear carb throttle spindle. When moving the throttle linkage
>from the gas pedal, I get the latter behavior (slippage). Of course
>at idle when the throttle spindles are resting on the idle stop
>screws, none of this matters; it only affects the mixture when the
>throttle is depressed.
30 degrees sounds a little excessive. Are the little 1/4" screws that
secure the spring-thingies to the throttle linkage tight? Mind you, there
is supposed to be a few degrees of throttle action before the throttle
plates move (not sure why, but things just don't work right if this is
not the case.)
>Because of this, when the throttle pedal is depressed, the front
>carb's throttle plate is further open than the rear throttle plate.
>I presume this may be causing a rich mixture in the rear carb at
>speed (?) which could be responsible for my engine misses?? This is
>speculation, and I haven't really figured out how the mixture is
>controlled in enough detail to figure this all out for sure.
I have seen this problem. In my car, however the car seemed to have a
vibration under power. Especially at around 4000 RPM's. What was happening
was that the front carb (in my case) was not opening correctly. Thus,
only 3 cylinders were getting the "correct" fuel/air mixture. Resolving
this problem resulted in many smiles on the driver's part.
>Last night, I replaced the spindle coupling with the one from the
>spare set of carbs. This one has no play in it whatsoever. Not
>only that, but the mechanism which allows a few degrees of travel
>from the throttle control rod before the throttle shaft begins to
>turn is rusted stuck. (TRF, Moss, and VB do not currently list this
>item.) Does anybody know if using that one with no slack permitted
>with respect to the throttle control rod will cause problems?
If there is no play in that part, the throttle is very "notchy". In
otherwise it is very hard to feather the throttle. You will notice this
as you cannot transition from no throttle to any throttle position without
lurching the car.
[stuff removed]
>While I had the plugs out, I finally performed a compression check.
>I found a variation from 110psi to 128psi. The low ones were #1
>(about 114 psi) and #4 (about 110 psi). #3 / #5 were the highest
>at 128psi, and #2 / #6 were at about 120psi. I am presuming that
>these figures are essentially close enough to indicate proper
>compression. I also tested #4 wet (after about 2 squirts of motor
>oil) and found 125 psi, so I may have some ring wear there (or, I
>suppose I may have not had the compression tester screwed in tightly
>the first time...)
Uh-oh. Well, if the car has a lot of miles, it could be ring time. I
wouldn't be too concerned. But you should keep an eye on this. Of course
you know to "open the carb dampers" when you do this compression test,
don't you? If you don't open the dampers, you might get erroneous results.
>--ken
>Kenneth B. Streeter | ARPA: streeter@sanders.com
>Lockheed Sanders | UUCP: ...!uunet!sanders.com!streeter
>PTP2-A001 |
>65 River Road | Voice: (603) 885-9604
>Hudson, NH 03051 | Fax: (603) 885-0631
bye,
rml
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