Jeep 4.0 Secondary Ignition Waveform questions

I also see the probes list when I click the Channel A icon, but no secondary ignition option.

Graveydavey wrote:

I don't see a probes menu in the software. I do have a Custom Probes list under the Tools menu, but I don't see a secondary ignition - inverted option on that list.

Maybe the probes menu is somewhere else. Any ideas? Thanks again.

The secondary ignition option is covered in the picoscope automotive software. You seem to be running the standard pico 6 software, not the automotive one.

Thank you! Downloading it now.

Ah, but it won't work with the 2204a. Bummer. I'll just need to figure out how to invert this waveform some other way.

There is a hack to make it work with the 2204A.....you'd need some modes dll' files that were on the internet for a while.

Why don't you just follow Chad's advice to apply a math channel , multiplying by -1? Do you know how to do that or does it sound unfamiliar to you?

Here is how to make you Probe with your Hantek Secondary clamp, inverted.

Thank you Wencraze for that walk through on how to set up the probe. Attached is a throttle blip that I took after I created the proper probe. I'd appreciate any and all opinions on this shot.

I retested the fuel pressure today and it seems good with the mechanical gauge. PSI was 30 psi. With a throttle snap it rose to about 35 psi then dropped to about 27 and settled back in at 30. Not too jumpy really. Pulled the vacuum line on the fuel pressure regulator and it rose to about 39 psi. the check valve held pressure for 25 minutes.

I'm not sure what to make of this problem. Jeep seems to run okay aside from the hesitation/stumble around 65-70 mph. The first attachment is a throttle snap, the 2nd is an inverted shot cruising when the Jeep is stumbling. The rpm doesn't seem to be interrupted when this happens, you mostly feel it in the seat.

I forgot to add these details to my prior post. Though the fuel pressure seemed to test well with the mechanical gauge at WOT it leaned out, ran below 1 volt (I didn't have a passenger with me to capture that waveform).

the plugs are clean even a little white on the electrodes.

Spark plug wires were all 4-5 k ohm in resistance.

Swapped coils again. No change in behavior. I did measure 12 ohms of resistance on the ignition control module. Kind of high, but that's not ridiculously high.

So I just re-read the whole post.

1. You got pictures of sparks.
2. Your fuel pressure looks good.

Though the fuel pressure seemed to test well with the mechanical gauge at WOT it leaned out, ran below 1 volt

In Global OBDII mode with a scan tool, you should see the B1S1 sensor reading between 0.1v(lean) and 0.9V(rich) and switching lean/rich, rich/lean once fully warmed up.

If you are pegged lean <0.3V at WOT you've got a fuel delivery issue.

Is the B1S2 also pegged lean under 0.3 volts as well?

I really wouldn't want to say much about the spark captures, because, for the most part, they could be normal at high rpm when there is lots of turbulence in the combustion chambers, but the others you have looked fairly normal, and it also looks like you upped the sample rate as well. So the first batch of pics was more than likely a sampling issue.

Also, it would be good to know what the fuel trims are doing at idle in park, then on a 65 Mph run.

Jumping straight to the scope isn't always the best scenario in driveability issues, the scan tool can answer many questions first, then possibly lead to oscilloscope testing.

Some scan tool data would be beneficial.

Unfortunately I can't plug a scan tool in because it's an 88. I believe the Snap On Mt2500 will read it, but I don't have one. It only has 1 o2, it's a titania type. 5v reference. It is switching back and forth, but that's all I can see. I was surprised to see it lean at WOT.

A couple of weeks ago, I was chasing this down as a trans issue.

I had been wanting to play around with a scope for awhile and this seemed like a good reason to pick one up. I wasn't sure if it was a misfire or not.

I just realized this morning that I misinterpreted the O2 sensor waveform at WOT. I double checked the service manual for the fuel injection system. On the 0-5 volt signal if the signal is closer to 0 the sensor is reading a rich condition. I had it backwards. The engine is running rich at WOT.

I think I should start looking elsewhere for the cause of my problem. I am going to test the rest of the sensors with the scope since I have it set up. I've test them all previously with my Fluke, but what the heck.

When the hesitation/stumble started, I thought it might be a torque converter lockup issue. I might take another look at that. I've been under the car looking around for indications of problem with the driveshafts, but I haven't seen anything out of the ordinary.

That makes sense as to why you went the scope route first, thanks for the explanation.

I drove the car again to play around the torque converter lockup. I wired in a switch that would cut the signal to lock up the torque converter. What I noticed was that that the stumble seems to be less when the torque converter isn't locked. It's still there, but its like the torque converter is cushioning it. That thought leads me back to a problem with the motor.

Here's another thought. I put remanned fuel injectors in when I reinstalled the engine. How would I go about testing them to make sure they are delivering the proper amount of fuel? Pulse time, I guess?

Is it normal for the firing line voltage to drop during a throttle snap?

Looking over these two waveforms again. I don't get what's going on. Why such different results?

Graveydavey wrote:

I drove the car again to play around the torque converter lockup. I wired in a switch that would cut the signal to lock up the torque converter. What I noticed was that that the stumble seems to be less when the torque converter isn't locked. It's still there, but its like the torque converter is cushioning it. That thought leads me back to a problem with the motor.

If you capture a waveform of the crankshaft position sensor, you can use the frequency of the signal to determine if the "fish-bite" is a misfire, or Torque Converter shudder. When you feel the "stumble", If it is a misfire, the frequency will drop. If it is TC shudder, the frequency will rise. Here is an image of crankshaft frequency with a vehicle with TC shudder.


When I felt the shudder, I manually pulsed a PowerProbe and captured it on the Green channel. The Black trace is the Crankshaft frequency, as I am accelerating. The big drop in the Black trace is a Gear change.

Is it normal for the firing line voltage to drop during a throttle snap? Looking over these two waveforms again. I don't get what's going on. Why such different results?

I believe, you are still under-sampling. You should be somewhere in the range of 1-3 million samples per second.

Thanks, Chad. A fish bite is a great description for this problem. I'll try this test tomorrow.

My attempt at capturing the crankshaft position sensor while the fish bite was happening didn't reveal much. Nothing dramatic like yours. I'm still learning how to manipulate these time and voltage settings.

I've been studying up a bit on fuel pump current testing, but the waveforms I'm getting don't look anything close to what a good pump looks like. Am I doing this right? I have a Fluke i410 clamp and I created a new probe in Picoscope for it. I set resolution for 10.5 bits because I'm getting a lot of noise. I think I have a bad fuel pump. Could anyone provide a second opinion for me? Thank you!

Graveydavey wrote:

My attempt at capturing the crankshaft position sensor while the fish bite was happening didn't reveal much. Nothing dramatic like yours. I'm still learning how to manipulate these time and voltage settings.

That is a good crank capture. And it is a good start.

(However, you have AC coupling selected. Even though the crank signal is an AC sine-wave, you should use DC coupling. AC coupling will hide the base voltage of the waveform. AC coupling is, primarily, used as a zoom feature. Pico's zoom capabilities are so good that AC coupling is, rarely, needed.)

The image that I posted was not a raw capture of the crank signal. It was the FREQUENCY of the Crank signal...an average of how fast the crank signal cycled from high to low, created with a "Math Channel".

The raw capture looks like this, WITHOUT the frequency math channel:


This is the same zoom level as the image of the PROCESSED FREQUENCY that I, previously, posted:


This is zoomed to inside of one of the green power probe pulses, which is close to the zoom level of your capture: