Yeah that is the screen shot function of the oscilloscope, it displays that reading in the status bar which I guess isn't shown that way, but it will record the test if I hit the right button and hopefully will show voltage in that form on here. I will do the test again since I need to test the high res signal still and I will try to capture the test in a different way so it will hopefully show more info. Its pretty easy to do and I learn more about the scope every time I use it.
low res pulse only between 1 and 2 volts ac when read from pin b of icm harness
1994 camaro z28 almost stock lt1 with a4, it should read between 1 and 4 volts ac with a multi meter when tested at pin b of the icm harness as the engine turns over, but mine only went up to 2.1 at the highest. I have the gm opti with only about 5k miles on it and I'm wondering if the problem could be that the optical sensor lens is dirty and if that could cause the problem so maby I can clean the lens and fix the problem because it's a non-vented unit. I would replace the cap and rotor with the msd "vented" verson. the car doesn't have any codes and it starts runs and drives but has a stumble at idle and hesitates when accelerating so it robs most of the power. I'm hoping I don't have to replace the whole unit since the one that's in there has such low miles on it. if anyone has any suggestions that would be great thanks.
61 - 68 of 68 Posts
To get more information on the screen for the low res pulses, slow down the sweep rate.
Al in Tucson
Al in Tucson
ok thanks I appreciate the input, I have been way to busy lately but I will get those tests done this weekend one way or another. Then I can hopefully get to fixing rather than testing for a change.
I tetested the low res wire from the opti and the high res as well now and from what I see they both look like they should, so more than likely my problem is somewhere else and it seems like its wiring or a sensor but I am at a complete loss of ideas at this point. I also could not find a way to make the scope display the volts that it was reading for either of the tests I did and not for a lack of trying. I need to mess around more with the software and see if I cant figure that part out but the square waves look like they should from what I can tell anyway. I think its odd that it doesn't display the volts right on the screen of the oscilloscope.
Scopes display volts like this. Somewhere you should see "Volts per division" for the channel you're using. Lets say, 1 Volt per division. 5 Volts would be 5 horizontal divisions. The divisions are faint horizontal lines. Another channel will use the same divisions, but can be different Volts per division. Most modern digital scopes will display the voltages, but the displayed voltage could be wrong. You still need to look at the divisions.I tetested the low res wire from the opti and the high res as well now and from what I see they both look like they should, so more than likely my problem is somewhere else and it seems like its wiring or a sensor but I am at a complete loss of ideas at this point. I also could not find a way to make the scope display the volts that it was reading for either of the tests I did and not for a lack of trying. I need to mess around more with the software and see if I cant figure that part out but the square waves look like they should from what I can tell anyway. I think its odd that it doesn't display the volts right on the screen of the oscilloscope.
Al in Tucson
ok thank you for that explanation because I am pretty sure I know how to change those settings it was just knowing what to change and with that I should be able to figure it out. Sorry I have been really busy and I finally have some time to mess with it again now and see what it says.
I know its been a while but I am still working on the car and I wanted to share what I have found out. I tested the high and low res signals from the optispark with my oscilloscope and they looked good for the most part but after thinking things through I wanted to look at the inside of the thing and see what was going on. so I took the opti off and took the cap off and the contact points were corroded enough where I wanted a new cap and rotor, then I took the rotor off and under it was full of rust, including a little on the optical disc. It is a gm opti with only a couple thousand miles but the car sat under a cover outside for a few weeks when I moved and during the time it sat, it rained alot so I'm sure that didn't help when I got around to picking the car up, especially since its a 1994 with an unvented opti. Since I already have a new vented cap and rotor from msd and the optical sensor is good I plan to get an opti from summit put the msd cap and rotor on it and maybe switch out the optical sensor from mine since it has the Mitsubishi version and I'm pretty sure the summit brand opti will use a cheaper sensor. when I get it all put together in a week or two I will post what happens but I think it will fix the problem. When I was taking it apart I also found the water pump bearing was very bad so I'm glad I caught that too.
Welcome back. Good luck with it.
Al in Tucson
Al in Tucson
61 - 68 of 68 Posts
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