Difficult Ignition Cutout Problem

[RattFink]

If it was clamped around the coil wire that goes to the distributor, that’s secondary ignition. Did the car act up while you were monitoring that?


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[cordes]

If it was clamped around the coil wire that goes to the distributor, that’s secondary ignition. Did the car act up while you were monitoring that?


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It did, but I wasn't able to see it with the trigger. I could record my screen while looking at it now. I'll give the car a drive tomorrow with that hooked up.

[RattFink]

Gotcha. Ahhh yes. The trigger. Imo the trickiest thing to learn about scopes. I feel like getting a good pattern on that coil wire is gonna tell you a lot. Good luck!!


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[cordes]

OK, is was very easy to get the trigger set and everything. I think the problem today was that my laptop was very unhappy in the heat of the car while trying to run the scope and OBS studio simultaneously. This thing was $100, so I'm still happy with it, though I may have found a pretty severe limitation.

Regardless, here is an interesting screen shot of the wave at one point, along with an admittedly poor video taken while I was just starting my drive before things froze up. I need to figure out how to stop the Xbox thing from popping up every so often too. That's annoying.

[chromguy]

What signal are you monitoring?

[RattFink]

Yikes. Did it act up when that screenshot was captured?

Also yes, OBS takes a lot of hardware resources. It struggled bad on my old laptop.


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[RattFink]

That screenshot to me looks like it is going very lean. You are losing spark duration due to a lean mixture. Unsure what cylinder or if it is all cylinders but highly suspect a lean condition.


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[cordes]

That was the ignition off of the coil when I just fired up the car and headed down the road. It doesn't run well until it is warmed up. Keep in mind that everything is out of the harnessbut thebare necessities.

ETA: what's more, I believe I had just swapped back to a stock computer and dropped the fuel pressure for the +40s.

[Shadow]

Do you have a wideband gauge in this vehicle?

[cordes]

Do you have a wideband gauge in this vehicle?

Not yet. I've just been trying to get it to run without the tach jumping about first.

[RattFink]

I keep forgetting the tach drops with it. Does it go all the way to zero?


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[cordes]

I keep forgetting the tach drops with it. Does it go all the way to zero?


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Sometimes it cuts out long enough to hit zero. Sometimes it goes down and jumps up super high. Other times it's more of a flutter. It always happens when the car cuts out.

[RattFink]

Working theory.
Fuel pump or injector issue causing intermittent lean condition. The tach is functioning as designed, just responding to the drop in rpm from the fuel issue. Fuel issues can feel violent.


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[cordes]

Working theory.
Fuel pump or injector issue causing intermittent lean condition. The tach is functioning as designed, just responding to the drop in rpm from the fuel issue. Fuel issues can feel violent.


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Could be. When it's really bad, the tach is not an accurate reflection of rpm at all. It could definitely be a bad injector too. If I replaced those, it was long enough ago that I don't remember.

[c2xejk]

Did you ever install a fuel pressure gauge?

[cordes]

No, I have not. That's going to be coming up soon.

[jeff1234]

Cordes, I don't know how much of your harness you replaced but I wonder if you have inspected splice# J2/4 in the harness by the coil.

[cordes]

Cordes, I don't know how much of your harness you replaced but I wonder if you have inspected splice# J2/4 in the harness by the coil.

If I'm not mistaken, I've inspected every splice in this harness visually.


I did some testing with my new amp clamp. I know that the waveform is upside down. I had the clamp on the wrong way. Just imagine the humps going up. Does this look OK? It seems odd to me that they draw a different peak current at times, but I'm not an expert. When I have it set to see just one event, they all look a lot more even. It was cool to see the hold time increase and decrease when I would rev the engine.

I also replaced the fuel pump. Perhaps it's a placebo effect, but the car feels a little smoother afterward. It was a very old walbro unit in the car.

[Shadow]

Have you replaced or swapped in a known hood o2 sensor yet?

[cordes]

Have you replaced or swapped in a known hood o2 sensor yet?

I put another NGK unit in there and it made no difference.

ETA: I just took a drive, and the fuel pump doesn't seem to have solved the problem, though it does run a bit better now. I'll pull a spare set of injectors and install them in the car tomorrow. We'll see what happens then.