Rough idle 2003 Toyota Highlander v6

[thejon]

When at stop at a stop light, I've noticed my wife's Highlander seems to vibrate, like the idle was low.. The idle doesn't seem rough and sporadic, just has a low hum and vibration felt throughout the car (only when stopped at a stop light). I'm attaching a pic of where the idle sits when stopped. I don't really know exactly what the lines on the rpm mean, if the 1st line past zero is 500, then it's between 500-800 I guess.
I've tried:
Cleaning the throttle body
New air filter
Sparkplugs should still have plenty of life left (iridium)
Cleaning the mass airflow sensor
Doing the "Toyota idle reset" floating around on the internet (did nothing).
What else can I do?
From what Google says, there's no way to manually adjust the idle but there is a cable like on the old cars, where you can adjust the throttle... Btw, novice city over here, which is why I'm asking on this forum. Thanks in advance.

 

[JohnnyJohnson]

You didn't say how many miles.

 

[burbguy82]

If you dont have a scanner......

The first thing I would do is look for a vacuum leak.

 

[zfasts03]

- compression check or cylinder balance test
- possibly counterfeit spark plugs that failed or a failing coil (more unlikely)
- run a quality fuel system cleaner through the system (Redline S1, BG44K, etc.), maybe a restricted/clogged injector

did this come on gradually or all of a sudden?

 

[benjamming]

Thread title says rough idle but the post says the idle isn't rough.
My first thought with vibration at idle is perhaps the motor mount going bad.

 

[The Critic]

Normal wear of the engine mounts. Don't chase after this unless you see an obvious issue. Otherwise, you'll spend a ton of money for minimal (or no) improvements.

 

[ripcord]

My first guess would be the idle air control valve (IAC) is carboned up or work out. Here's a video of someone changing one on an 1MZ-FE in a 02 Lexus.

 

[Rock_Hound]

I have a vehicle with the same engine. It has had a very small vibration at idle since new. It hasn’t gotten worse in 21 years and is just enough to feel and rattle my cassette tapes in their holders. You hear it a bit because the way the key FOB hangs it rattles a bit. Mine only vibrates when stopped and in drive at engine idle, if you put it in neutral or park, it goes away.

 

[kschachn]

Normal wear of the engine mounts. Don't chase after this unless you see an obvious issue. Otherwise, you'll spend a ton of money for minimal (or no) improvements.

As the owner of more than a couple of old cars, this is one of the first places I'd look.

 

[thejon]

You didn't say how many miles.

150,000

 

[thejon]

- compression check or cylinder balance test
- possibly counterfeit spark plugs that failed or a failing coil (more unlikely)
- run a quality fuel system cleaner through the system (Redline S1, BG44K, etc.), maybe a restricted/clogged injector

did this come on gradually or all of a sudden?

Gradually. I'll check out the Feul cleaners. I called the shop and they confirmed they installed NGK iridium.

 

[thejon]

Thread title says rough idle but the post says the idle isn't rough.
My first thought with vibration at idle is perhaps the motor mount going bad.

Sorry, should have said "vibration at idle". How do you check the motor mounts?

 

[thejon]

I have a vehicle with the same engine. It has had a very small vibration at idle since new. It hasn’t gotten worse in 21 years and is just enough to feel and rattle my cassette tapes in their holders. You hear it a bit because the way the key FOB hangs it rattles a bit. Mine only vibrates when stopped and in drive at engine idle, if you put it in neutral or park, it goes away.

Same. It's only when in drive, foot on the break at a stop light. It goes away when in park or neutral. Did you ever figure out what it is?

 

[thejon]

If you dont have a scanner......

The first thing I would do is look for a vacuum leak.

We used to spray carb cleaner around the engine to see if the idle went up... Is that how you do it? How do you check for a vacuum leak?

 

[burbguy82]

We used to spray carb cleaner around the engine to see if the idle went up... Is that how you do it? How do you check for a vacuum leak?

I do the spray thing sometimes, but it always does not work. Another safer way to do it is with propane and a hose.........

You just get a length of hose and attach it to the end of a torch, then go around to all the possible areas of a leak, I have found that to be more reliable.

The end all be all IMO, is a vacuum gauge. Typical NA engines make about 18-20 at idle. If you are less than that, It is likely there is an issue. That number might be slightly different on your engine, not sure.

I suggested vacuum leak because it is easy to detect, and cheap and easy to rule out.

 

[Rock_Hound]

Same. It's only when in drive, foot on the break at a stop light. It goes away when in park or neutral. Did you ever figure out what it is?

Was told by a Toyota master tech that it was normal over 20 years ago. I have driven other 1MZfe equipped vehicles and they all have a little vibration in this situation. Nothing has changed in 22 years of operating mine, so I don’t worry about it.

 

[lbhsbz]

If you dont have a scanner......

The first thing I would do is look for a vacuum leak.

a vacuum leak would cause a high idle.

 

[lbhsbz]

Motor mounts. Replace them with OEM (aftermarket are trash...don't waste your money or time)

You have 4. One on the trans/driver's side, one forward and rearward of the engine on the subframe that supports the weight of the engine, and then a torque arm on the passenger side.

 

[Marcozi]

a vacuum leak would cause a high idle.

and fluctuating idle revs.

 

[lbhsbz]

and fluctuating idle revs.

Depends if it's a fluctuating vacuum leak or not