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What was the issue when you started misfiring/flashing CEL?

Old 07-06-2019, 05:53 PM
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phreaktor
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Default What was the issue when you started misfiring/flashing CEL?

My 04 Z started this immediately after a rear brake job attempt tonight (lower caliper guide pins are seized ugh). Iím thinking itís the weirdest coincidence ever as they have nothing to do with each other, but I digress.

I know this can be attributed to a fouled plug or bad coil pack/MAF sensor according to what Iíve read here. I am taking it to Auto Zone to have the codes pulled tomorrow but I want to get ahead of this. I know it was already throwing a code for an O2 sensor and camshaft position sensor. Is this related to the cam sensor code or a whole separate issue considering the CEL is now flashing for the first time? What is most common culprit in your experience? Thanks!

Torrey

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Old 07-06-2019, 11:28 PM
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813_350Z
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For starters, there is no way your CEL/misfire is related to your brake job.

Not sure what to say about this question though. The problem will be, well, related to whatever your CEL indicates. It could be from your camshaft sensor or it could be from a bad plug. Pull your codes and start from there.
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Old 07-07-2019, 10:05 AM
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I have a 2003 350z (that I bought new). I've experienced misfiring; and the causes were crankshaft position sensor, camshaft position sensor, and coil pack. All three were diagnosed correctly by codes read by Consult.
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Old 07-07-2019, 02:31 PM
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Had misfires 2 different times. Both times they were only showing as random misfires. The first time I lazy and just changed a few coil packs till the issue was fixed. The second time (2 yrs later), I used Cipher and turned off each cylinder 1 by 1 until I found the one that wasn't firing and a new coil pack fixed the issue.
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Old 07-07-2019, 06:32 PM
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Usually a coil pack. Most of the coil failures I've seen are caused by oil in the spark plug tubes, which was remedied by replacing the valve cover and coil.
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Old 07-07-2019, 06:43 PM
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Thanks guys. I didnít make it to AZ today but I will update tomorrow when I get the codes for future members reference.
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Old 07-08-2019, 03:53 PM
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Ok so here are the current codes: P0305 and P0037. For some reason, itís no longer throwing the Camshaft Position Sensor code thatís its had for a year or so that used to cause the car to stall and limp. Does the P0305 (Cylinder 5 Misfire) supersede the CPS code or something? Can the misfire be caused by that sensor or is it more likely to be the coil pack and or spark plug? Also which physical O2 sensor is Bank 1 Sensor 2?

Scan results
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Old 07-08-2019, 04:03 PM
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i8acobra

provides very good advice here. I replaced two ignition coils before discovering that the valve cover and gasket was the culprit needing replacement. After replacing these parts, my problem went away. I'm guessing but do think you have a problem with the ignition coil. Depending upon your car's mileage, you might want to consider replacing the valve covers and gaskets.

Originally Posted by i8acobra View Post
Usually a coil pack. Most of the coil failures I've seen are caused by oil in the spark plug tubes, which was remedied by replacing the valve cover and coil.

Last edited by Spike100; 07-08-2019 at 04:04 PM.
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Old 07-08-2019, 08:47 PM
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Pull coil #5, check if the bottom is wet with oil. If it is, replace the valve cover and coil. If it's dry, swap it with coil #3. Clear codes and drive. If the misfire moves to cylinder #3 (P0303), then the coil is bad. If it doesn't move, check the plug. If it's good, swap injectors #3 and #5. Again, if the misfire moves, it's the injector. If not, it's time to do a compression and leak down test. A bad crank sensor will trip a P0300 multi-cylinder misfire, not a single cylinder.
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Old 07-11-2019, 04:45 AM
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I pulled plug 5. Threads are covered in oil. Gap is still set at 0.043. Getting ready to swap coils with cylinder 3.

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Old 07-11-2019, 04:47 AM
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Coil is dry btw.
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Old 07-11-2019, 05:33 AM
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Code is now P0303! Bad coil. Thankfully one is en route. Canít tell you guys how much I appreciate this forum! 😎💪🏾
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Old 07-11-2019, 06:54 AM
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Originally Posted by phreaktor View Post
Code is now P0303! Bad coil. Thankfully one is en route. Canít tell you guys how much I appreciate this forum! 😎💪🏾
Codes do not indicate failed parts. what so ever...



If you plugs look like that you need new valve cover. and gasket.
or you will just continue to missfire due to the oil on the plug/boot in the well.
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Old 07-11-2019, 07:05 AM
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Originally Posted by masterjr33 View Post
Codes do not indicate failed parts. what so ever...



If you plugs look like that you need new valve cover. and gasket.
or you will just continue to missfire due to the oil on the plug/boot in the well.
The code went from P0305 to P0303 when the coil was moved from cylinder 5 to 3. The code itself doesn't mean the coil is bad, the fact that the misfire followed the coil is what means the coil is bad. That being said, the coil went bad because of the oil in the tube. That much oil on the spark plug socket means the coil tube had oil in it. Replace the valve cover. It's also a good idea to replace the plugs too, since you're there.
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