Strange Current waveform?

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Senior_Citizen
Newbie
Posts: 5
Joined: Tue Feb 23, 2021 11:36 pm

Strange Current waveform?

Post by Senior_Citizen »

Hello,

I took a waveform off all the injectors on a 1996 Mercury Marquis 4.6L. Two of them show a strange current waveform, (image attached). Could anyone help guide me on how to interpret this? All the rest of the injectors looked normal, but 5 & 6 looked like this.
Attachments
1996 Mercury 4.6L Fuel Injector 5 Strange Current.JPG
1996 Mercury 4.6L Fuel Injector 6 Strange Current.JPG

liviu2004
TwoWaves
TwoWaves
Posts: 472
Joined: Sat Mar 19, 2016 8:23 am
Location: Netherlands

Re: Strange Current waveform?

Post by liviu2004 »

Interference, measuring mistake, bad injectors, connectors resistance, who knows.
What does the resistance measurement say?

ronw38
TwoWaves
TwoWaves
Posts: 65
Joined: Sun Aug 27, 2017 8:00 am

Re: Strange Current waveform?

Post by ronw38 »

For good interpretation always send live files not screen shots, ch A is injector and looks OK ch B looks like ignition or interference, use channel references and notes to state the situation. I assume the vehicle is running OK and you are just looking at patterns, for fault diagnosis use a longer time base and zoom in ? In short your post offers little to work with. Cheers Ron W

Senior_Citizen
Newbie
Posts: 5
Joined: Tue Feb 23, 2021 11:36 pm

Re: Strange Current waveform?

Post by Senior_Citizen »

Thank you both. Sorry for my late response. I guess I don't have my settings right on the forum to send me notifications of responses. I'm going to have to learn more about how to post my actual waveforms. I did retest and moved my amp clamp around to different positions and it did lessen the 'noise' in the waveform, yet it still showed more noise on those two cylinders than the rest. I also realized I had my amp clamp upside down on the posted pictures. The car has an intermittent misfire, (not misfiring at the time of the scope test), and high fuel trim under load. Tested all the coils, injectors, and fuel pump. Nothing jumped out at me as being the smoking gun. But this car has been good for me.... Most extensive use of my scope so far and I've learned that not every back probe is a good probe... not every clamp is a good clamp. Lack of experience and user error are some of my problems, but it's good for me to see my mistakes as I've tested this car.

ronw38
TwoWaves
TwoWaves
Posts: 65
Joined: Sun Aug 27, 2017 8:00 am

Re: Strange Current waveform?

Post by ronw38 »

Hi Sen Cit I think you are using a2204a scope which is near useless for automotive diagnostics ! an automotive scope gives you the ability to examine the spark firing line in detail [misfires]using experience to determine spark failure, tracking, lean misfire etc a good scan tool and scope plus experience is a must and for positive experiences you need the right tools keep trucking with what you can measure just be aware of the limitations to find answers Cheers Ron W

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