#3 plug is fouled (black and sooty) the other cyl good. Engine has misfire. Why?

Asked by May 04, 2017 at 02:07 PM about the 1975 Triumph Spitfire

Question type: Maintenance & Repair

Engine is misfiring and number 3 cyl plug is black ( fuel fouled) I have
replaced wires, plugs, etc. compression is 115 +/- 3lbs in all cylinders. Why is
number three acting up?

3 Answers

74,385

Have you replace the cap and rotor? Make sure you are getting good spark at #3. A hotter plug might reduce the fouling and a high performance coil could also be a good idea.

74,385

I am assuming that you have the stock 1 carb set up. If you have dual Webers or something else then one carb may be out of adjustment.

26,525

WET OR DRYPLUG DOES THE MISS GO AWAY WHEN A NEW PLUG IS INSTALLED? ..DOES IT USE OIL..DID YOU ALSO DO A LEAK DOWN TEST/VALVE SEALS OK ON THAT CYLINDER?

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