I ve got a misfire on my vectyra at all engine speeds, on closer inspection I found that number 1 and 2 plugs not firing. I had the diagnostic machine pluged in and it said cylinders 1 and 2 misfiring.
I ve replaced the big coil pack (second hand item) on top of the plugs and replaced the plugs but I still have a misfire on cylinders 1 and 2 any ideas anyone?
Is the integrity of the second hand coil pack certain? If not try again! That said, coil packs normally start failing in the low RPM/high load area of operation. Try tightening the gap on the affected spark plugs. A smaller gap will require the coil pack to operate at a lower peak voltage. If the plugs don't fire with a small gap, and the resistance readings for the coil pack terminals are ok, the problem lies elsewhere.
Meh! Single electrode spark plugs are cheap. I Like the freedom to run smaller than recommended gaps-takes the load off coil packs-which aren't cheap.
?? Might as well just run the ECU mapping from a totally different car!
Reducing the plug gap will reduce the voltage at which it fires, giving incomplete combustion, poor fuel consumption, increased emissions and making the engine work harder which puts a strain on everything.
By paying MORE for spark plugs, I used Bosch Quads on my Vauxhall Ecotecs, changed at the recommended 40,000 miles and got 100,000 miles without any sign of stress on the coil pack
And make you less attractive to the opposite sex while you're about it.
I can't comment on the ecotec, but I average considerably better than the official fuel consumption, car sails through the MOT emissions test, and has a stable idle. Spark plug is set to .0.03", tiny by today's standards. Engine is on original coil packs after 120,000 miles...
The idea that a big gap gives faster combustion is fanciful. If the mixture is properly prepared, a tiny gap is perfctly sufficient. A big gap is a band-aid to poor mixture preparation. If you need it, use it, otherwise set as low as you can without misfiring at idle.