running around 90k now, had this code pulled. the car runs fine, seems so anyways. have ran multiple tanks of fuel, mpg hasnt changed. any idea what the culprit coudl be?

i was thinking vacuum leak but dont see anything loose. could use some help.

 

Are you sure there are no secondary codes....Sounds like one of the coil packs is breaking down.

 

Check all cylinders if they are firing. Start with the basic first. Injectors would be next.

 

Find out which cylinder is misfiring. Once that has been found move the ignition coil to another cylinder. If the misfire code re appears determine if it's the cylinder you moved the coil to. Then replace the coil. This is what I did. If not at least it eliminates one variable.
Chris

 

whats the best way to test the cylinders?

 

Keep driving until you get an error code other than P0300. Until you see a P0301 through P0306 error it will be hard to track down. All P0300 tells you is random misfire.

In the meantime you can look at other possible causes. Do you run premium fuel in your RX? If not, run a few tanks or perhaps put some injector cleaner in a tank of fuel. Sales currently running at Advance Auto Parts and AutoZone for Chevron Techron.

 

its been well over 1500 miles now, already ran fuel cleaner and we have never run premium in it, just 87 for the past 30k miles. ill see if its the same code still. i just filled it up again and mpg is still what it usually is which is hovering right about 20mpg.