ipaniwala

So …I changed the spark plugs on my 2004 GX470.
Engine runs smooth. Idle inside cabin can't even be heard . Its very responsive and performance on driving is smooth and car feels peppy.

Issue is , millage has dropped to 12 miles/gallon compared to 15.5 miles/gallon I got previously .
I have changed 8 spark plugs and air filter.

One mistake I made was not to check the gaps on the spark plugs but they arrived undamaged and with a covering so I had presumed that gaps would be setup correctly.

Between changing spark plugs and air filter has anyone else notice a drop in fuel millage ?

chiph9

If you used NGK plugs, I've never seen one that wasn't gapped correctly from the factory. I've stopped checking (seems to be pointless).

I did notice a drop in mileage, but it recovered over time. Not sure if it's because of the plug change, or a change in my driving habits (new plugs! Wooo!)

Chip H.

ipaniwala

Getting back to my old millage now.
I have Denso plugs …I think the computer just took time to adjust.
After about 300 miles it's slowly back to old millage and engines purrs like new again…very happy with this simple DYI

River19

Are most people going with iridium plugs on the GX?

I have the 4.7L in my 2001 Tundra (non VVTi) and DIY swapped in iridiums about 40K miles ago and have been very happy. Dealership wants all the money to replace them........which always makes me laugh.....

chiph9

I've had cars in the past where I installed "performance" plugs and performance actually went down. You're better off installing either of the OEM plugs - NGK or Denso.

Chip H.

River19

Roger that. Why spend the coin for iridium if it isn't needed........

Thanks for the quick answer

ALAN553

OEM PLUGS are iridium, that's why they last as long as they do.

Listers

Just completed my spark plug change at 101k. Denso SK20R11 is what came out and it is what I replaced it with also. Also took the chance to change the air filter for a K&N OEM replacement.

anyoldiron

..........totally unnecessary to take of airbox if you have 4" Extension, knuckle and 1' extension.

foreste1

Just finished my plug replacements, used Denso Iridium. I will say be so careful about that small screw holding coil tube over plugs.....I tightened too much on my SC and broke it off in valve cover, what a nightmare to drill out!! On the GX, I only tightened by hand until tight and then gave just a slight turn with socket, be careful!! Also so weird one of my coils when I pulled it the tip completely fell off so I needed to replace that coil pack, $90, but oh well, its done.
My idle is running high, but I think it needs time to come back down, as I did clean throttle body while I was in there.

techrep

Just changed the plugs/boots and springs, cleaned throttle body and MAF sensor @ 73K miles. Wow ! Great results

freddiekd

Well thanks for reminding me. I have 144,000 + and passed time to change. Nice write up also.

freddiekd

Don't forget to blow out the spark plug hole before removing plugs. It's probably already been mentioned but didn't read all replies. Good clearly written post. Thanks.

Teslee

Hey Guys,
I've got 08 GX470
I just ordered IK20TT Denso Spark Plugs because I have 9mpg in the city lol.
The gaps on IK20 and SK20R11 are 0.43" and 0.44" while on IK20TT it is 0.39". Does someone know if they are going to be fine on my car or I should order IK20?

Thanks

chiph9

You should go with the OEM spec NGK or Denso iridiums. I wouldn't try and guess a different heat range or gap.

Chip H.