Low idle issue?

My 4.0 auto is idling somwhere between 560 and 600 rpm

When the rpm drops below 600 I can feel the engine run rougher.

I did change the head gaskets recently but the truck has been doing this since before that.

New plugs, cleaned out the throttle body and MAF along with new PCV valve and hose. Went through the throttle position sensor reset procedure.

When driving the truck feels very smooth, its just at idle.

 

550-600 sounds about right for hot idle in drive, usually around 600-800 in park.

 

If I disconnect my battery for more than a few minutes my truck will idle rough for the first 20-30 minutes but it goes away if I just keep driving the truck.

 

Havent disconnected the battery recently and its been doing this for a bit.

I thought idle was 650-750?

 

In park yes but in drive or reverse usually 550-650

 

I guess the problem is some where else then.

 

You may want to check out your motor mounts they are prone to breaking out of the frame on 05 and 06 trucks, that could cause a vibration at idle.

 

Why do you try to do a throttle reset, look it up in the forms

 

I do when I grease the U-joints, this has been happening for at least a few years now. Thought it would go away when I freshened up the engine while I did the head gaskets but it hasn't.

Tried that, I also do that every time I disconnect the battery for something.

 

How many miles on the plugs?
What plugs are in it?

Also, Toyota says “650-750” Transmission in Neutral.

I’ll also add, my truck also idles low(er) in gear. Around 600 or so.
If what you are feeling is kind of like a miss, but not a hard/full miss, that seems to occur every 20-45 seconds? Mine does this too. But it should be noted, I’ve never cleaned my MAF, cleaned the TB, or changed the PVC. It’s done this since I got it with 24k miles. I’m at almost 150k now.
95+% of the time, I run 87 octane (E10).

Annnndddddd

 

Pretty much exactly what it feels like, but no misfire codes. Checked with a reader and cylinder one is counting a few misfires but not enough to feel like this and they don't correspond to the stumble. Seems to match when the RPM drops below 600.

Plugs are new, Denso K20HR-U11, changed earlier this year.

In the last 6 months ive had the injectors refurbished, cleaned MAF and TB, new PCV and hose, along with new timing chains/tensioners/guides. Replaced my head gaskets so I just did everything I had access to while I had the heads were off.

I run 87 all the time, tried 91 once to see if it made a difference. It didnt.

Everything feels good on the truck except for this, sometimes is worse sometimes its better.

Its really more an annoyance, and its done it for a while. I actually cant remember when it started but I bought the truck new and it didn't do it then.

 

Sound about like my truck.
Never hooked a scanner to it to see if it’s misfiring.
While I do try to help people out a lot. The majority of my experience in repair, is from things needing repaired. Simply put, I don’t fix thing until it needs fixed or is causing an issue. In my case, I have no issue with this “misfire” feeling.

Is it normal?
I don’t know.

Is it a problem?
I don’t, mine has done it for years with no attempts to fix it.
The truck is doing everything I ask of it. Therefore, I’m leaving it well enough alone.

 

I just find annoying when I do notice it at a stop light. I really started to notice the difference when my buddy got a 4runner with the 4.0 and his is smooth at idle, I should see what his engine idles at

Replacing the head gasket got me on a kick of doing a bunch of stuff on the truck ive been putting off, both repairs and mods and this is one of the last things to tackle. Its been doing this for years. If I cant figure it out im not concerned, it would just be nice to know whats going on.

 

I understand completely.
If it bothers you too much. Slide it up into Neutral.
That seems to “fix” mine. - I have an Auto, this bumps the idle up.
Problem goes away for me.

 

A lot of older toyotas idle low when hot. It's fine don't worry about it

 

OP, did you ever sort this out? Have similar symptoms.

 

Nope.

I recently swapped out all the O2 sensors while replacing a bad cat and it does it less now but still happens.

 

When you did your head gaskets, did you have the heads resurfaced?

 

Yes, but the heads were flat so they just took skim cut to clean them up. According to the head shop they were almost perfect and almost didnt believe I had that many miles on it.