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Spark plugs - 2007 Lexus ES 350

I’ve had the car since new and this just started happening 3 years ago. I would get the VSC, anti-slip and engine light and the car I could feel was misfiring. But what I did notive is that i was getting 560 miles per tank wersus 430… WOW I didn’t want to correct it but I knew the engine wasn’t right. I changed to plugs and a coil here or there from the auto zone diagnostics tool-3 of the sparks posts were gone, I didn’t use the iridium. But I’ve gone through this 3 times now. It has to be something sending the voltage to the sparks. What do I need to look at, besides getting the shop to charge me 3 checks?

I suggest using ONLY the exact spark plugs listed in the owner’s manual

Either go to the Lexus dealer, or have a shop order the correct ones for you

Don’t let auto zone talk you into buying the ones they have in stock . . . UNLESS those are exactly the ones listed in the owner’s manual

How many miles . . . ?

any of the spark plug boots visibly damaged?

coil(s) visibly damaged?

you did replace the plenum gaskets when you replaced the plugs the first time, I hope . . . ?!


I’ll check with the oem, i do replace the plenum gasket. I’ve got 260k miles on this and i want to drive it till it stops working. The spark comes were changed 6 months ago, though this time i didn’t use oem. I figure if i go to the parts store and read the code it will be another spark plug. I was wondering if it was a device sending the voltage erraticly.

Coil failures are seen more on the 2007-2008 ES350 and RX350 than any other year. What were the fault codes from your ECU?

Could it be the cat converters clogging?

If you are referring to the top of the spark plug that the boot or coil-pack plugs onto, if that part is being damaged or destroyed by running the engine, make sure the electrical contact there is good. If it isn’t a good electrical contact the spark will occur there and at the tip of the spark plug, which could explain both the misfiring (from a weak spark) and the damaged spark plugs.

The damage was at the post under the arc. I had an alternate plug then and that’s when i noticed my mileage was great. I just got the ecu read and our shows po304 only

P0304 is a misfire on cylinder number 4. Upon removal does the number 4 spark plug look different than the other three?

Suggest taking a close look at coil #4 . . . is it cracked?

Might not be a bad idea to perform a compression test on #4 cylinder

If there’s low compression, best to know now, versus throwing lots more money at the problem . . .