Sage Advisors,
Have been having a bit of a time trying to find the cause of a miss I
experience when backing off the throttle, or crusing at 2,000 to 3,000
rpm. There is also a slight popping from the exhaust as the throttle is
let off during shifting. Accelerating and higher speed cruise has no or
very little miss.
1980 Spit.
-Lumenition System and Distributor checked out
-Fuel pump tests fine
-Fuel filter has been replaced
-Coil has been changed out with test coil from other smoothly operating
spit.
-No fouled plugs
-Plug wires have 1 K on them
-Timing set to factory specs.
-Engine, carb, emissions, and exhaust are all at original factory stock
-No apparent vacum leaks
A likely culprit seems to be the by-pass - deceleration valve. I went
through the Haynes and Bentley procedures for adjustment. When the
vacum line is removed from the distributor, the rpm rise from 800 to
1,000. When plugged, it doesn't rise enough to register on the car's
tach. According to the manuals, it should rise to 1,300 rpm, or higher
if out of adjustment. I attempted adjustments to see if it would change
the plugged rpm, and several turns of the screw in either direction
yielded no results. I think it may be a bad valve, but would it be
causing the miss....?
Any thoughts welcomed!
Thanks!
Mike P
1980 Spit
1979 Spit
|