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Toyota Service
Toyota Service, Toyota Expert
Category: Toyota
Satisfied Customers: 4601
Experience:  30+ Yrs of auto experience, Award Winning Svc. Manager; Just Answer Customer's Choice Award Winner
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1997 avalon 1mzfe, rough idle after 35 min od driving and

Customer Question

1997 avalon 1mzfe, rough idle after 35 min od driving and po300 cel
Submitted: 11 months ago.
Category: Toyota
Expert:  Genchi Genbutsu replied 11 months ago.

Thank you for allowing me to help you with this concern today and am sorry to hear that this is happening. I will have to ask you a few questions so that I can get a better understanding as to what may be going on with your Avalon.

The P0300 code is for a misfire related issue. Are there any other codes stored beside the P0300?

What brand spark plugs do you have installed right now and when were they last replaced?

Customer: replied 11 months ago.
No other codes and they are ngk dual electrode plugs.
Expert:  Genchi Genbutsu replied 11 months ago.

Ok the dual electrode plugs are not the correct application for this vehicle.

Did this P0300 code happen before or after you installed these plugs?

Customer: replied 11 months ago.
Before
Expert:  Genchi Genbutsu replied 11 months ago.

And how soon after replacing the plugs did the P0300 code return? Immediately?

Customer: replied 11 months ago.
after about 40 minutes of driving.
Expert:  Genchi Genbutsu replied 11 months ago.

Ok, then I would start with putting the correct plugs into this Avalon and clearing the codes. I doubt the problem will be much more than this.

Customer: replied 11 months ago.
What are the correct plugs?
Expert:  Genchi Genbutsu replied 11 months ago.

Ok, it looks like the information I have is incorrect as the dual electrode plugs are the correct application. Please allow me to opt out and let another expert step in. Thanks

Expert:  Toyota Service replied 11 months ago.

Hello. Different expert here. Please allow me to add some input here. The correct plugs are Nippondenso ("ND") PK20TR11. NGK work, but they do not work great, in my opinion. Conversations with Toyota engineers have resulted in the input that the engines are actually designed to a specific spark plug. If the gap is off, and the plugs are NGK, you will have a host of misfire issue. Get these at any Toyota dealership. Let's talk about the wires and the oxygen sensor. Did you use genuine Toyota parts? If not, it is proven that non-Toyota sensors, plugs and wires do not work well in this engine. If your wires and sensor are not Toyota, I would purchase and install the factory ones. On cleaning the MAF, make sure that you have no leaks anywhere on the intake tubing. Make sure the MAF is properly seated where it fits. Then clean the throttle body with aerosol throttle body cleaner. Wipe out any black Greasy material that is found inside the throttle body and on the throttle plate. These are the things I woudl be doing if your car was in my shop. If you have any questions, please feel free to reply. Thanks.