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Coil current ramp question

posted May 06, 2016 16:05:38 by George
My friends 2004 Nissan Quest 3.5 Lt van is running rough and asked me to take a look at it, and found that cyl. 3 is not contributing, but since it is located under the manifold I tough I ask you guys what you think of this capture, and what could be causing this(whe can take as long as we need, the car is at his house a few blocks down and its been siting there for about 3 weeks)

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14 replies
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George said May 06, 2016 16:10:32
I think its a feed wire issue, but I don't know if a bad spark plug or coil boot could cause this kind of ramp, and since this is not really a shop's customer, but a friend's car (not charging), I would like to learn something fixing his van.
Thank you for your time.
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AndyMacFadyen said May 06, 2016 16:51:32
If they are similar to the smaller Nissan engine I work on it is a 3 wire coil, ISTR once you have access the coil there are resisstance checks you can do.
Wiring damage is possible a cause so do power and ground checks and check the coil is getting a nice clean switch om/off signal on the centre terminnal but my money would be on the coil I have changed a couple on the 1.4 Nissan Note engines.

What ever you do take the plug out and examine it and compare with the others for additional confirmation you are working on the correct cylinder. I generally replace the plug on the affected cylinder as a matter of course.
[Last edited May 06, 2016 16:52:26]
"Rust never sleeps"
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George said May 06, 2016 17:11:06
Yes, 3 wire coil, but there under the manifold. I'll follow the harness to gain access to the 4 volt turn on signal latter today if I have the chance. Meanwhile, any more suggestions are welcome so I can do as much testing when I get there. Thanks
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Chris said May 07, 2016 02:12:05
You know your control is there because it tries to ramp but flat lines. That suggests your power and ground are present also. It's coil time. Voltage drop the ground and make sure the power feed will light a regular test light. Generally when there is a bad power or ground the current ramp will have a lot of hash in it. They way the waveform plateaus suggests that the primary is not capable of maintaining current flow open or high resistance. A shorted one will show a very high current draw.
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Tyler said May 07, 2016 13:47:06
That's a great capture! Never seen a COP with that kind of current ramp before.

I'm with Chris, this looks like a high resistance issue to me. Once you get the intake off, I'd suggest using a small bulb (tail or brake light) across the #3 coil power and ground, at the connector. This will load the circuit heavily enough to expose any resistance issues.

If the bulb shines brightly, then I'd say it's coil time. New plugs are a good idea, like Andy said.
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George said May 10, 2016 14:51:14
Thanks guys, I'ts been busy here and I haven't had a chance to go and do any more testing, but I will definitely do what you guys have suggested so far and post the results.
Thank you.
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Tyler said May 10, 2016 17:45:13
No worries, thanks for keeping us updated!
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AndyMacFadyen said May 10, 2016 19:07:38
Thinking about it the control transitor built into the coil could be what is called a Darlinton Pair, that ISTR is a circuit where a transistor triggers another transistor to switch high voltages and currents, my guess is one of the transistors has failled limiting the current.
[Last edited May 10, 2016 19:08:33]
"Rust never sleeps"
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Tyler said May 10, 2016 23:45:10
Thinking about it the control transitor built into the coil could be what is called a Darlinton Pair, that ISTR is a circuit where a transistor triggers another transistor to switch high voltages and currents, my guess is one of the transistors has failled limiting the current.


Oooooh, good thought Andy! This would explain the geometric flatness of the abnormal current ramp.
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George said May 11, 2016 18:10:27
Right on the money.
I took the manifold off (it's easy), and swapped coils to the front cylinders and the weird ramp moved with the coil, here's a capture.
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George said May 11, 2016 23:47:25
Here's the finish product (and notice the aftermarket coil amperage diference).
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Tyler said May 11, 2016 23:58:37
Good looking captures, sir!

Any codes reappear after coil replacement? I ask because Nissans are notorious for setting a P1320 when aftermarket coils are installed, misfiring or not. NOT trying to say you were wrong to install a Duralast, just curious if this Quest is happy with the new coil.

Side note, for anyone following along, there actually is a ScannerDanner video that covers a similar issue on a Honda. Same premature current limiting symptom was found in that video.
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George said May 14, 2016 07:16:04
Any codes reappear after coil replacement?

Not yet,I gues we'll find out (after about 2 weeks of not being used, i'ts now a daily ride).

NOT trying to say you were wrong to install a Duralast, just curious if this Quest is happy with the new coil.

No worries, I like constructive criticism because that's when we learn.
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Tyler said May 14, 2016 14:27:22
Not yet,I gues we'll find out (after about 2 weeks of not being used, i'ts now a daily ride).


Awesome, glad to hear it! This is good info to have, especially when an OE coil may be significantly more expensive.

No worries, I like constructive criticism because that's when we learn.


Agreed.

To be honest, I also asked about the Duralast coil because I've had (surprisingly) good luck with them. I've known VW Passat's to spit codes with other aftermarket coils, but were perfectly happy with a Duralast.

Not sure what it is about their design/construction that keeps the PCM happy in these 'sensitive' applications, but it works!
[Last edited May 14, 2016 14:28:21]
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