1st and 4th Cylinder misfire

adkfinn said:
I understand that people haven't had/heard of coil failures with these engines but my Saab would go through coils (quality Bosch parts, very similar design) every 75k mi. Most of the time these coils would still produce a spark and the OBD would not throw a code, but a good data log would show elevated KR values for the cylinder in question. Symptoms were cold start hesitation, decreased fuel economy, etc. I would basically replace plugs and coils at a 75k interval on that car. Your symptoms sound similar to failing/weak coils to me. The primary culprits are typically the ones closest to the firewall, presumably due to the higher temperature levels. Apples to oranges here I know, but I thought it was worth chiming in.
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Thanks for the insight. Toyota motors don't tend to go through coils at an accelerated rate. I am throwing a code for misfires on 2 and 6 so I'm going to replace those coils first. If the symptoms persist I might have to invest into all 8 or just take it to a shop for a diagnostic. I'm sure I could solve it myself but I don't want to waste a sum of money replacing things that don't need to be replaced. I'm expecting delivery of my new coils for cylinder 2 and 6 today so I'm currently prepping my truck so it's a quick easy job when it gets here.


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On that note, I decided I'd go through and get a few pictures of some stuff to note for our fellow 4.7 motor owners. One is the position of the PCV. It's under a sort of rubber cover so it could be tough to see at times. It's located on the driver side of the motor above cylinder one, here's a picture for reference.
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And here's what it OE Aisan part looked like
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And here it is relative to the cheapy I got to hold me off till I order a new aisan one
IMG_0018.JPG

I went through and pulled the connectors off coil 2 and 6 and broke the torque on the bolt holding it down. I didn't pull it out because I don't have the coils in hand and I wanna keep it sealed till they arrive. That's all I got as of now, I didn't take any pictures of the throttle body and am not in the mood to pull it apart to get some. Will report back later today on the coils.




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Bad news sort of. Idle shudder is gone completely but I still get shudder when accelerating. It actually got worse than it was before I did the new coils. I guess it's a 1 step forward and 2 steps back right now because one issue is solved and the other is worse. Next step is check the injectors I guess. I need to drive it till the check engine light is on so I can run codes again and see if any things new


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So update on the situation. Ran the codes when the check engine light came on. Misfire Cylinder 7 now, however 2 and 6 are gone. Sort of a step in the right direction I guess


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TrueBlue said:
So update on the situation. Ran the codes when the check engine light came on. Misfire Cylinder 7 now, however 2 and 6 are gone. Sort of a step in the right direction I guess


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Hey imma thread jack back...my CEL is back on after 4 days...awesome.


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3eyedRaven said:
Just a light, drives and runs fine from what I can tell


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That's weird, I'll try to read up on what it could be for you, I've got work in a little though so I probably won't be able to respond till later today


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TrueBlue said:
Yeah hopefully it'll only be the sensor, I've got a bad cat on mine so I've got that damned P0420 code all the time. At least your misfiring is gone though right?


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No doubt. What is the cost/process to replace the cat? Havent researched it yet.


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3eyedRaven said:
No doubt. What is the cost/process to replace the cat? Havent researched it yet.


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Uhh a lot more than I wanna pay right now haha, I have the skills to install the new cat but a new one is like $400-$600 I think. I'm probably just gonna run a cat less downpipe with o2 simulators and shortie headers at some point next year


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3eyedRaven said:
Appreciate you checking in. I haven't had the time to work on it yet. Have been traveling for work lately.


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Ah, we'll do report back when you've solved it haha, I have the same code on mine and all new sensors so I'm curious if you find some way to fix it that I overlooked


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TrueBlue said:
Ah, we'll do report back when you've solved it haha, I have the same code on mine and all new sensors so I'm curious if you find some way to fix it that I overlooked


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Well, CEL cleared itself. I wonder if the O2 sensors were accustomed to reading inaccurate data from lack of efficient combustion from those old plugs. Now that the plugs are new and the engine is running 'optimally', it has relearned?? #speculation #wishfulthinking


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