On Wed, 05 Feb 1997 10:14:19 -0800 James Sudduth
<james.sudduth@autodesk.com> writes:
>At 11:37 AM 2/5/97 -0600, you wrote:
>>> Now the car has developed a (new) definite misfire which
>appears
>>> to be getting worse. This misfire occures mostly under gentle
>>> throttle around 2000 rpm, but appears to diminsh with increasing
>>> throttle and rpms.
>>>
Thought I'd jump in here and relate a story on a tuning problem that
nearly drove me nuts. My 72 TR6 has a 75 engine. I had it rebuilt and
put it back in the car expecting great things. Wrong. Performance was
really poor and sometimes it didn't want to run at all. Went over the
ignition system and everything looked okay. Put in all new wires,
points, whatever. Ran every test I could think of and finally decided
the problem MUST be carburetion, so I tackled the carbs - checked needle
numbers and springs - the works - no good. Even bought a second set of
carbs out of sheer frustration. For weeks this went on with the car
running lousy. Took the head back off just to look around. No help.
Put it all back together. Same problem.
While I was standing next to the running engine, listening to it
struggling to idle, I realized I could hear the spark jumping from the
rotor to each pole in the distributor. Seemed kind of strange and I
couldn't recall being able to hear that in any other engine I had worked
on, but this was very distinct. I rechecked the timing and then I looked
very carefully at the relationship between the rotor and the poles on the
distributor cap. Huh? When the ignition fired, ther rotor was pointing
to a spot in between two of the poles on the cap. It turned out that the
retard diaphragm had apparently swollen up, perhaps from fuel
contamination, and was pushing the breaker plate in the advance direction
to the point that the distributor geometry was totally screwed up. The
spark was having to jump a huge gap, which became worse as the mechanical
advance came into play, perhaps even jumping to the wrong pole at times.
I took out the retard diaphragm and fabricated a metal rod to take its
place which held the breaker plate in the right position. It was like a
miracle. The car came to life and has given 10s of thousands of miles
flawless service since.
Mark Anderton
1972 Triumph TR6 (Getting ready for paint)
1984 Jaguar XJ6 (2 ea - some people never learn)
1967 Jaguar XKE 2+2
1966 Morris Minor (everything a car should be)
1971 Land Rover (Farm use)
1967 Daimler V8 Saloon (Be patient! I'm workin' on it)
1958 Velocette MSS (500cc single)
1987 VW Golf GTI (How did that sneak in here?)
1972 Grady White Chesapeake Mercruiser I/O
|