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Discussion Starter #1
I am hoping someone can help me with this issue. My van has 140K miles. I replaced 6 spark plugs with Denso Iridium a month ago. Now, the engine is a little shake when driving with 3 lights stayed on (AWD, Engine Check, and Trac Off). My OBDII shows three codes (P0302 P0304 P0306) on bank 2.

What could be the problem? I replaced the ignition coil on cylinder #6 just to test. But the OBDII still showed the same trouble codes(P0302 P0304 P0306).

Thanks
 

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If the car was perfect before you replaced, definitely is related with the spark plugs you did. At least two possibilities, if you did them perfectly (torque etc..), maybe the plugs are counterfeit? Indeed, some experts here will give you some idea soon..
 

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Where did you purchase the spark plugs?

Check all your electric connections from the spark plug change. I think it's highly unlikely that coils went bad at the same time you replaced spark plugs.

My guess is either there's a connector loose or missing or the plugs are counterfeit.

-Mike

Sent from my SM-G950U using Tapatalk
 

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Probably erroneous but it's a simple look and see. On my 6 cyl Olds the injectors are divided with two fuses. If one fuse blows the car still runs but only with three cylinders. Knowing this fact saved me from an expensive towing when an injector shorted out the entire circuit. I pulled the fuse from the 1/2 with the short and limped home on three.
 

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P0300 is defined as Multiple Cylinder misfire, RPM speed uniformity variance. P0301 thru P0306 define specific cylinder misfires based on the cam/crank position sensor data that corresponds to where in the rotation the speed variance occurs.

Fortunately, all 3 affected cylinders (2 / 4 / 6) are up front. Odd that all 3 are bad. Check your wiring harness to see to see if it got damaged?
 

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Discussion Starter #6
Thanks for all the responses. I bought 6 plugs (Denso Iridium Long Life FK20HR11 3426) from AutoZone. They are the same as original Toyota plugs.
Yes, cylinders 2 4 6 are up front. It took me several hours to replace the three plugs in the back. It’s really difficult to access them.

The tab on the electrical wire connector to the ignition coil (cylinders 2 4 6) broke off easily. But they’re still plugged in snugly. See picture.
Could the culprit be the camshaft timing oil control valve assembly bank 2?
46435
 

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Looks like your front injectors are easily accessible. Plugging the wires from an injector onto a noid light will tell you if the injectors are getting a signal. It'll blink.
 

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pull the coils and carefully check that they are clean and free of any signs of arcing along the outer surface and inside the boot (use a bright flashlight). Be meticulous about your inspection because it can take a detailed eye to see signs of arcing on the coils. You may have to pull the plugs as well and check them for signs of arcing as well along the ceramic insulators. Do not wipe the parts down before inspecting them.
 

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Thanks for all the responses. I bought 6 plugs (Denso Iridium Long Life FK20HR11 3426) from AutoZone. They are the same as original Toyota plugs. Yes, cylinders 2 4 6 are up front. It took me several hours to replace the three plugs in the back. It’s really difficult to access them.
The tab on the electrical wire connector to the ignition coil (cylinders 2 4 6) broke off easily. But they’re still plugged in snugly. See picture. Could the culprit be the camshaft timing oil control valve assembly bank 2?
I purchase a lot of stuff from Autozone and Advanceauto but I not sure I would trust them for some of the most critical components on my vehicle. If inspection does not show up anything concerning, you should start by swapping the front cylinder plugs with the ones that you replaced and see if the problem goes away.

Regarding broken tabs, it is fairly common as the plastic starts to dry and they become brittle over time. There is a specific way you have to remove them (push down first to alleviate the pressure on the tab, then gently press the tab and they pop right off). You can however easily repin these with new ones, just need to source the blanks.
 

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Discussion Starter #11
pull the coils and carefully check that they are clean and free of any signs of arcing along the outer surface and inside the boot (use a bright flashlight). Be meticulous about your inspection because it can take a detailed eye to see signs of arcing on the coils. You may have to pull the plugs as well and check them for signs of arcing as well along the ceramic insulators. Do not wipe the parts down before inspecting them.
I pulled the coils and the spark plugs. Inspected each one carefully. I found one spark plug from cylinder #4 with broken ceramic insulator. I bought a replacement plug from Autozone and replaced it. Autozone scanned again. It is now showing P0302 cylinder 2 misfired and P0304 cylinder 4 misfired. It doesn’t display P0306 anymore. It’s strange.
 

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Discussion Starter #12
I purchase a lot of stuff from Autozone and Advanceauto but I not sure I would trust them for some of the most critical components on my vehicle. If inspection does not show up anything concerning, you should start by swapping the front cylinder plugs with the ones that you replaced and see if the problem goes away.

Regarding broken tabs, it is fairly common as the plastic starts to dry and they become brittle over time. There is a specific way you have to remove them (push down first to alleviate the pressure on the tab, then gently press the tab and they pop right off). You can however easily repin these with new ones, just need to source the blanks.
Thanks I will try that.
 

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Discussion Starter #13
Is that the only codes? Gut feeling is you have a air\fuel sensor going south on you.
Yes, the OBDII Scanner now shows P0302 cylinder 2 misfired and P0304 cylinder 4 misfired after I replaced one cracked ceramic plug in cylinder 4. Not sure how to check air/fuel sensor.
 

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Discussion Starter #14
8A256F06-0FCD-4329-820E-E5E0774850BC.jpeg
The spark plug on the left from cylinder 4 has a cracked ceramic insulator. I replaced it today. I replaced 6 plugs recently and they had already looked really dark and dirty. Something isn’t right.
 

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Compare with the old ones if you still have them. It is xtremely wrong by the visual color of those plugs. They should look very light brown or very light grey; indeed should not dark like that. The old ones I assume were the genuine ones for sure.
Double check the Part Number of those plugs. Sometime, store such them they are selling many different brands and type while actually the best for this car should be one number only.
 

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Do NOT buy at amazon.com for very sensitive items because it is selling so many product from china mainland (the communist one); buy it on your local toyota dealer or toyota dealer online.
 

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Since the codes are for front plugs (you lucky dog) which are easy, see if you can dig up the old plugs. You might try those as they were not throwing errors as I understand all this. Three plugs from some other source might not be too much cost to shoulder just for a test, as well. I hate rear plugs.
 

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Reading these Sienna spark plug posts always gives me anxiety. I’m not an engineer and not extremely mechanical. So why did they make what was at one time the easiest task ever - to replace spark plugs - with the hours long drudge it has turned into? Not just for the DIY warrior but for the dealer mechanics too.

Even I managed to replace the plugs on my 1970 V8400, the carburetor fiasco however I won’t ever discuss 😄
 

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Discussion Starter #19
I checked the plug wiring several times. They are secured
I bought the inline ignition tester at Autozone. The cable is too short. It can’t reach the spark plug. I ended up returning it.

The van was running fine before I changed out the plugs. I checked the park number on the plugs. It matched the original plugs.

I still don’t know what wrong with it. I don’t want to give up yet.
 
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