I recently changed my spark plugs on our 98 gs300, the car has 150k. It ran fine for 100 miles or so after the plug change. Then it started missing, and gave a code p0303. I have swapped coil packs around put the old plugs in, replaced the wireset, in many different combinations. To no avail. Can anyone offer any suggestions before I take it to the dealer? The ecu has been replaced once before. at 90k. Thanks in advance!

 

did you replace with the recommended plugs?

did you try clearing the code after putting the old plugs back in?

 

Yes, replaced with oem original part number denso plugs. I cleared the codes with a code reader, and also disconnected the battery cables for about 15 minutes.

 

That code deals w/cylider or plug #3 unless one of the other ones are setting off the #3 wire.The only thig I can tinnk of is maybe a broken/short igniter wire. but since you've swapped them out I'm at a lost.

 

Thanks to all who have provided suggestions. I am going to go out and change the plugs back to the old ones, previously i only changed the #3 plug. I will see if the car just does not like those plugs. Thats the only thing i have left to try. Cannot make it into service for a few days.

 

I did not change plugs after all. Wife took it in to the dealer, but on the way there, she said it mysteriously stopped the misfire problem. Being that i had reset the ecu, a couple days ago. The tech could not find any codes when hooked up to their reader. They also road tested and could not reproduce the problem. Who knows what the problem is/was, but they gave it a clean bill of health and sent her on her way.

Will see if the problem comes back. Thanks to all!

 

Good deal.It has a mind of it's own