Curious secondary "mega"-spike!!

AlexMpico · Post by **AlexMpico** » Fri Mar 04, 2022 1:06 pm

Observed some curious secondary ignition measurements today on a coil on plug Volvo V70 5cyl engine. Using another brand, the scope sometimes defaulted to a ridiculous 150kV+ peak firing line. I'm thinking Impossible. No coil can produce that even open circuit even once. Im thinking the scope is not doing the math of 1:10,000 attenuator properly from the Inductive probe (I'm using a HT wire extention between COP and plug) ... so I try the baby Pico just for comparison ... get a good wavefore 9kV-12kV at idle, good burn line etc, scope correctly set to 1:10,000 attenuation ... then suddenly on one coil I get the same phenomena. Huge firing line, apparently, and massive lean nose at end of burn line ... I'm pushing the plug connection down to ensure connection, I'm pushing the coil boot connection in to ensure connection, but it continues. Reconnect from the top later, and it's a good waveform again. Am I crazy? Any thoughts on what's going on??

victor2k · Post by **victor2k** » Sun Mar 06, 2022 4:01 pm

Hello,
Maybe a good connetion to ground will help ,sometimes the capacitive/inductive probes need it.
Best regards

PicoScopes
& kits

For vehicle manufacturers

EV kits and
accessories

Noise, Vibration and Balancing

Milliohm tester

Pressure sensors

Current clamps

Breakout
leads/boxes

Accessories

Automotive Forum