Which to do first- spark plugs & coils Or O2 sensors

My new for me 05 has a 167k miles with unknown service history. Carfax shows 8-9 dealer visits with very little detail so I’m assuming no gross neglect, but can’t be sure.

Given the chassis has no rust I want to fix as many issues and update as much as possible. I plan to keep her for a long time. PHM’s reinvestment build is a huge influence and inspiration albeit my skills are a fraction of his.

https://www.tundras.com/threads/the-professional-hand-model-reinvestment-‘build’-a-chronological-story.46816/

(So far I’ve replaced timing belt/tensioner/pulley and WP; I’ve updated a bunch of old interior and exterior bulbs mostly with LEDs; I’ve greased driveline.)

now for my question. Next item I plan on doing is either spark plug & ignition coils (as needed) OR replace four O2 sensors. FYI I have a P0420 code which reads “catalyst system efficiency below threshold”.

My inclination is to do plugs first since a) it’s a maintenance item anyways and b) I think it’s easier to do and given I’m rusty with wrenching it’ll give me some practice. The other part of me says to do the O2 sensors first since that’s more relevant to the error code. Any thoughts ?

 

Do your spark plugs, replace your air filter as needed, clean the MAF and replace the downstream 02 sensors. If you want to confirm it’s the sensor beforehand, swap the 02 sensors on each side and see if it tracks from one side to the other.

Oh, and only use Denso or get them direct from Toyota although only Denso makes them for Toyota.

Edit: Use NGK plugs since you own a 2005 and not a 2002.

 

thanks, this makes sense.

As far as MAF cleaning how often do most people clean on FGT? I know it differs from car to car. I had a b13 Sentra SE-R that MAF would gunk up if I sneezed from inside the car
and I’ve had cars were after 30-40k miles it’b squeaky clean inside.
FYI as of now 100% of miles have been on pavement.

 

My plan for coils is I’ll do them all when the 1st one fail. Denso from RockAuto.

I did plugs on my truck at 207k when I got it. Almost all the plugs were loose and creating blow by at the plugs and all my coils were burnt, puffed and split/ cracked.

I replaced the rubber coil items with ones from NGK and put the coils back in as they were not misfiring. I am now at 320k with the same coils and still running strong.

 

Have you replaced plugs since 207?

 

I clean mine every so often but if you’re throwing a code which could be airflow related, it’s best to help rule out those components. An exhaust manifold leak could also be a source of the problem.

 

Plugs in your truck are 100k mile plugs. Your manual will tell you which model to buy. Get the NGK brand, which should be iridium. Don't bother unplugging the coil packs, just remove the screw, slide out the coil, and set on top of the intake. Don't use anti-seize on the plugs. Don't over-torque.

Grease your driveline. Hell, read this, since this guy has about 70-80k less miles but all the info applies. It'll tell you how to do MAF too. Expect to dump 1/4 - 1/3 can of MAF cleaner into it. ONLY USE MAF CLEANER.

Never replace coil packs. Not unless they fail.

Never shop for parts at scAmazon, fleaBay or WallyWurld, you will get counterfeit parts. It's ultra-common these days for cars, appliances, damn near anything.

O2 sensors, if P0420 you only need to do upstream and downstream on the driver's side, bank 1.

Check for oil leaks! Especially around the block, under the valve covers, below timing overs, down the displtick, on the inside of skid plate, etc. Confirm torque on the valve cover bolts.

 

Oh man thanks for that thorough response. Much appreciated.

I was considering replacing ignition coils preemptively until I read above. Why do you recommend against? Is it uneeded, or new ones not as good or maybe new coils don’t jive as well with a well seasoned engine? Thx

 

Some guys on here didn't see the 1st one fail until 250k-300k miles. If you really love throwing away money, you do you, I guess? It's unusual for one to fail, much less two at the same time. Me, personally, I'm waiting for my 1st one to fail, and I'll replace that one coil only, then the next when the next fails. You'll get a cylinder-specific OBD code when one dies, so it's not like it's rocket science to figure out which is toast.

The tubes on the coil packs have a penchant for hairline cracks. Don't let it scare you. Plenty of guys on here have them - me included on a couple - and have never once had spark jump. I've seen some dudes on here replace any/all with cracks on the tube proactively. I personally ... they're f'n expensive, no thanks. If they work, they work!

PS - You don't need to gap iridium plugs. IIRC, the instructions actually tell you not to gap, due to potential damage of the electrode tip. In case you're not aware...

 

Yup iridium should come with 1.1mm gap.

 

To go along with what @shifty` said, if you're worried about a misfire just order 1 or 2 new coils and keep them in the truck. That's what I did.

 

O2 upstream sensor is tough to reach. I'd replace the downstream one and see if your code goes away. (worked for me) Buy denso from rock auto

 

No, I’m over 320k now. MPG’s have dropped to 15.8-16.4. So she could probably use some plugs, $hit I don’t remember the last time I changed the air filter maybe close to 207?

It’s hard to do maintenance when she’s running so well lol. Still burns the 285’s

 

Going to be replacing my plugs soon does anyone have the part number for the NGK plugs?

 

The below is from 05 Owners Manual….

For those using Denso, there's a typo in the Owner's manual. It should be "SK" not "KS"


https://www.tundras.com/threads/1st...and-maintenance-schedules.91566/#post-2753128