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This may be irrelevant but I thought I would post it. I have a 2006 V6 Camry. Same thing, same codes. I would reset the code and everything would run fine for a year in the beginning, then to a few months, then to a few days and then the reset would not work. After the reset and driving the car for about 30 miles, the car cleared emissions test with no code. I did not want to spend a lot on an old car. Eventually, after going through a long think, I changed the front bank oxygen sensor. This was about 2 years ago. All fine - no problems after that, no codes. Cost me about 60 bucks to get a new sensor from Advance Auto Parts. As I said, it may be irrelevant, but this is my story.
 

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Just for reference, I noticed after replacing coil-packs several times that the noise suppressor attached to the mounting bolt (front driver side bolt) on the coil pack was shorting out to the frame of the coil pack (the frame should not be grounded). I clipped the corner off the suppressor mounting tab after the last coil replacement and the problem permanently went away!
98906
 

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I second Andreas' recommendation to check the spark plug wells for oil. My ATQ engine had the same issue with the driver's side valve cover gasket leaking oil into the plug wells causing a misfire on the #6 cylinder. The misfire happened at startup after the car sat in the cold for a week.

The CEL for Cat efficiency below threshold could be triggered by a misfire, but the long term solution is to install the spacers. I was surprised how easy it was to install a single spacer on each O2 sensor. No P0421/431 codes since.

While Techron helps, a thorough injector cleaning can be done by almost anyone with basic skills. Running the car without the fuel pump fuse in place removes the pressure from the fuel rail. The rail is held in place by 4 screws and is easy to remove. You can spray brake cleaner through the injectors using a 9 volt battery to open the solenoid. At 200K+ I would also replace the injector seals (2 on each injector). I have not experienced another misfire since replacing the leaking valve cover gasket.
 

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The CEL for Cat efficiency below threshold could be triggered by a misfire, but the long term solution is to install the spacers. I was surprised how easy it was to install a single spacer on each O2 sensor. No P0421/431 codes since.
That is a workaround, not a solution. if you live in states with emissions inspections (Like CA and NY), you will fail your inspection.

The solution is to find out what is wrong.
-Are your cats shot? 200k is a reasonable limit on their life (yes technically its life of the car, most cars don't make it that far before they are tossed).
-Are your 02 sensors good?
-do you have other underlying issues that are causing misfires?
-etc etc

Spacers are not a long term solution.
 

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Do they actually look under the car on a lift? You can not see the spacers on the V6 otherwise. They worked long term for my V6 as it had the "artificially low setpoint" issue from VW. A flash was available for certain 2000-2001 V6 ECUs, but it was not free if you had over 100K.
 

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Just for reference, I noticed after replacing coil-packs several times that the noise suppressor attached to the mounting bolt (front driver side bolt) on the coil pack was shorting out to the frame of the coil pack (the frame should not be grounded). I clipped the corner off the suppressor mounting tab after the last coil replacement and the problem permanently went away!
It seems to me that you were changing the wrong parts, if the suppressor capacitor was shorted the whole time. For the suppressor cap to work, it has to be grounded, which I expect the Aluminum coil frame is. The suppressor's purpose is to transfer high-frequency electrical noise to the car's body-ground, rather than have that ignition noise affect radio reception. If it was defective and internally-shorted, then it could have made the coils seem defective, which were probably fine all along.
 

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- Changing the Coil Pack is an EZ DIY job
- Enough (real) misfires without fixing the cause could end up fouling the catalytic converters.
- I had some oil in the spark plug wells that caused misfires - vacuumed it out with a shop vac using the flat nozzle, put a plastic straw on one side of the nozzle and block the rest of it with a finger (& hold the straw firmly so it doesn't get sucked into the vac - guess how I figured out that part)
 

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Discussion Starter #48
  • Changing the Coil Pack is an EZ DIY job
  • Enough (real) misfires without fixing the cause could end up fouling the catalytic converters.
  • I had some oil in the spark plug wells that caused misfires - vacuumed it out with a shop vac using the flat nozzle, put a plastic straw on one side of the nozzle and block the rest of it with a finger (& hold the straw firmly so it doesn't get sucked into the vac - guess how I figured out that part)
Thank you for this information.

My mechanic checked the spark plugs on the driver side from the top (under the black plastic cover) and said its not leaking. He did not check them from underneath of my car. I will ask him again to check the spark plug wells on the driver side.

IMG_5941.JPG
 

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It seems to me that you were changing the wrong parts, if the suppressor capacitor was shorted the whole time. For the suppressor cap to work, it has to be grounded, which I expect the Aluminum coil frame is. The suppressor's purpose is to transfer high-frequency electrical noise to the car's body-ground, rather than have that ignition noise affect radio reception. If it was defective and internally-shorted, then it could have made the coils seem defective, which were probably fine all along.
The frame is not at ground! The screw and the suppressor tab is at ground. If the tab touches the frame it is a short that will cause the pack to malfunction. When it is not shorted you can measure voltage between the two! Once you blow the coil pack it must be replaced.
 

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The frame is not at ground! The screw and the suppressor tab is at ground. If the tab touches the frame it is a short that will cause the pack to malfunction. When it is not shorted you can measure voltage between the two! Once you blow the coil pack it must be replaced.
You can see that the frame is insulated from ground by rubber bushings!
 
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