Rough idle after tune up

Replaced my plugs two weeks ago because of a rough idle. Put new ones in and it went away. Old ones were shot, obviously. Now that rough idle has returned only it's not as frequent. It comes and goes. RPM'S fluctuate about 200 at idle in park. What gives?

 

Clean your throttle body and mass airflow. Its should help

 

How many miles? Those plugs were shot

 

235k miles. I'm pretty sure these plugs might have been original lol.

 

Assuming 4.0L engine - V6. There are some vacuum hoses on the drivers side. Make sure all are attached to their intended location and that none are cut.

 

Those are supposed to be replaced every 30k miles!

 

Remove the battery terminals and allow your idle to re-learn when you do a throttle body cleaning .
With high mileage vehicles , you may want to look at your ignition timing .
The overhead cam chains are known to stretch .
All kinds of youtube videos on this .
Here is an example
https://www.youtube.com/watch?v=UR50da0sDOc

 

Well I bought it with 230k miles on it so its unknown when or if they were replaced the last time.

 

FYI 09 plugs are 100k interval per book and mine looked good after 100k.
After cleaning items above add a bottle of injection cleaner once in awhile too.
Usually has methanol in it to capture any water in gas too as ethanol does not do it.

Note next post #10 is misleading - sorry ethanol mixes with water but does not capture it like methanol and then allow it to be burned off. Dry gas is methanol.
Ethanol corrodes the fuel system that's why its limited to 10% and reduces your mileage by 10% - what a useless additive pushed by the corn growers.
See:
https://www.theglobeandmail.com/glo...lem-with-ethanol-in-gasoline/article29103634/

 

Actually yes it does. And most gas today already has 10% ethanol mixed in with it. Adding more alcohol such as methanol to your gas to "remove water" can actually make matters worst as it will dilute your gas and make it absorb much more water and exasperate the idle problem that op already has. I would highly advise against it.

 

If they were original and you have a V6; youll have 3 NGK and 3 Denso plugs.
What they do in the 4 banger I have no idea.

Edit:
Is it throwing a code? Could have burned out a coil with that huge gap in the plugs.

 

No codes have been thrown and yes 3 NGK and 3 Denso's came ou . So its sounds like they may have been original.

 

If you have the 1GR-FE it’s every 30,000 miles.
It you the 2TR-FE it is 100,000 miles.

Does it needed them every 30k?
Well, that’s not for me to say.

I just drive my truck. Lol

 

I agree with cleaning throttle body insides and MAF, plus a healthy dose of fuel injector cleaner in the gas tank. Provided there are no vacuum leaks.