Kiliona
Well-Known Member
- Joined
- July 12, 2013
- Messages
- 213
- Reaction score
- 43
- City, State
- Idaho
- Year, Model & Trim Level
- 1992 Ford Explorer XLT
Alright so here is the deal, I have a 1992 XLT. It started off having issues idling and starting especially when hot. From there it moved on to be very hard to accelerate from a start, right now the vehicle only starts half the time and is VERY low on power when it does run.
I am an automotive student and believe i've run all the preliminary checks, it's had a good tune up, fuel pump, coil, plugs, wires, fuel filter, etc etc. I have tested the CPS using an oscilloscope and it gives a very good looking waveform, no issues.
So This is what I need help with. If someone has experience with an oscilloscope and waveforms it'd be very useful to me.
I will attach two pictures, the first one will be the waveform that should be coming out of, and going into the ignition control module (ICM). The second one will be the waveforms I am seeing coming out and going in. The second waveform, the green/black line is the SAW if I remember right. The third waveform, the blue one, is the CPS signal, the SIN waves being the teeth on the tone wheel, the TAN wave being the missing tooth or TDC on number one. And the last line, the brown one is just a sync connected to a spark plug wire, I don't remember which one. The top line, the red one, is supposed to be the PIP signal (profile ignition pickup).
Now what these waveforms tell me is that ONE: all of the inputs to the ICM seem to be good. The CPS has a good signal, SAW is fine, I know it has new coils plugs wires and etc. Basically all the inputs to the ICM are good, but when you look at the PIP signal... it is absolutely fubar'd from what I can see. You can see on my first picture the PIP signal should be a digital signal, and should look similar to the SAW signal but less width. Logically if all the inputs to a module are good, the ground is good, but the output is bad, the module needs replacing.
So where I am at now is trying to decide if I trust this diagnosis enough to spend 150 dollars on a new ICM (poor college student), or whether I may be missing something, or set up the oscilloscope wrong in the first place. I am looking for input to see if anyone agrees this is a good diagnosis. I do realize not many people use oscilloscopes as diagnosis tools and it's kind of obscure to some, so I apologize if this whole thread made no sense.
I am an automotive student and believe i've run all the preliminary checks, it's had a good tune up, fuel pump, coil, plugs, wires, fuel filter, etc etc. I have tested the CPS using an oscilloscope and it gives a very good looking waveform, no issues.
So This is what I need help with. If someone has experience with an oscilloscope and waveforms it'd be very useful to me.
I will attach two pictures, the first one will be the waveform that should be coming out of, and going into the ignition control module (ICM). The second one will be the waveforms I am seeing coming out and going in. The second waveform, the green/black line is the SAW if I remember right. The third waveform, the blue one, is the CPS signal, the SIN waves being the teeth on the tone wheel, the TAN wave being the missing tooth or TDC on number one. And the last line, the brown one is just a sync connected to a spark plug wire, I don't remember which one. The top line, the red one, is supposed to be the PIP signal (profile ignition pickup).
Now what these waveforms tell me is that ONE: all of the inputs to the ICM seem to be good. The CPS has a good signal, SAW is fine, I know it has new coils plugs wires and etc. Basically all the inputs to the ICM are good, but when you look at the PIP signal... it is absolutely fubar'd from what I can see. You can see on my first picture the PIP signal should be a digital signal, and should look similar to the SAW signal but less width. Logically if all the inputs to a module are good, the ground is good, but the output is bad, the module needs replacing.
So where I am at now is trying to decide if I trust this diagnosis enough to spend 150 dollars on a new ICM (poor college student), or whether I may be missing something, or set up the oscilloscope wrong in the first place. I am looking for input to see if anyone agrees this is a good diagnosis. I do realize not many people use oscilloscopes as diagnosis tools and it's kind of obscure to some, so I apologize if this whole thread made no sense.
