To make sure there is no regular or intermitent current leakage from the new leads or plugs run the engine on idle in the dark and any current leak will show up as blue spark jump or blue halo around the plug/s and or leads [Yes even new ones]. If you see a blue spark or halo on or around any part of any lead don't touch the lead as it packs a wallop. Switch off and remove the lead/plug then try re-fitting if still the same then take the full set back to the shop and tell them what's happened on the site test.
No spark/halo showing try the following.
1. If your Engine misfires at idle speed
then check out the following
1.1 Worn, faulty or incorrectly-gapped spark plugs
Note: the new ones might not be gapped properly
1.2 Faulty spark plug HT leads
Note: even though they are new they can be faulty.
1.3 Vacuum leak at the inlet manifold or associated hoses sucking in excess air.
1.4 Blocked injector/fuel injection system fault
1.5 Uneven or low cylinder compressions
1.6 Disconnected, leaking, or perished crankcase ventilation hoses
2. If your Engine misfires throughout the driving speed range then check out the following
2.1 Fuel filter choked
2.2 Fuel pump faulty, or delivery pressure low
2.3 Fuel tank vent blocked, or fuel pipes restricted
2.4 Vacuum leak at the inlet manifold or associated hoses
2.5 Worn, faulty or incorrectly-gapped spark plugs
2.6 Faulty ignition coil
2.7 Uneven or low cylinder compressions
2.8 Blocked injector/fuel injection system fault
robert whiting, January 2005
