Hi, as stated in title, I have a misfire/hesitation under heavy load, feels like a plug/lead breaking down. I've checked the lambda - ok, also no fault codes, so thought I'd get the scope out. Attached are the four patterns, obtained by using the coil extension lead & HT pickup lead on channel A & channel B on the coil trigger. Not the pattern I was expecting on any cylinder but also worried about the interference on cylinder 3. I swopped coils & spark plugs but interference remained. I haven't checked the wiring back to the ECU & haven't checked the primaries with the scope yet, just thought I'd open up conversation now.
Vehicle: Fiat Marea 1800cc 16v 2001 Hitachi injection
To start with I would use some basic diagnostic skills - such as whether the ignition coils are getting power and ground and finally I would see if the coil on plug are receiving a good trigger signal from the ECU.
A fairly easy way to check the functions of all the ignition coils in one simpel test - is to use a current clamp around the common feed supply to the coils. The ignition coils are getting power from the fuel relay - so if you can find this relay it shouldn´t be difficult to make this test.