2001 nissan altima high idle after warmup

“Boyet” post=155620]I saw the middle leverage moved slightly from cold start to warmup,
[color=#ff4400]But did the idle arm stop come to rest on the adjustment screw?
Is there any rust or corrosion that might be binding the spring assembly or any other parts from moving freely?[/color]
can I adjust the screw (with the red arrow) ,to see if the idle goes down? ”
[color=#ff4400]You could but ….
99.9 times out of 100 that adjustment screw has not moved.
The issue (maybe) what is preventing the idle arm stop from coming to rest onto the idle adjustment screw[/color]

also btw I got p0420 engine code , this came out suddenly(not sure if because I cleaned the idle air control valve?) thx
[color=#ff4400]There are a number of things that could be causing this p0420 catalyst efficiency code. The most common thing is the catalytic converter itself is no longer functioning properly. The other likely thing is the rear O2 (oxygen) sensor is no longer working properly. Other things could include exhaust leaks, damaged exhaust pipes, damaged O2 sensor wiring/connectors, plugged catalytic converter, etc.

The easiest thing to do first is a visual check of things. Visually inspect the exhaust system for leaks, check the catalytic converter for dents, holes, severe discoloration, and check for a rattle inside. If any of those symptoms are there, the converter likely needs replacement. Then, visually inspect the downstream O2 sensor (behind the converter). Check for broken wires, obvious faults, etc. If all that checks out, you’ll want to check the operation of the O2 sensor. To do that, you’ll need access to a scan tool or oscilloscope. Check that the waveform is pretty steady. If the reading fluctuates then the sensor is likely bad and will need to be replaced.[/color]
(the upstream o2 sensor maybe the culprit? still original part 88K miles) thank you.
Read my response above

Is this correct for your exhaust system?

If so
#4 is called a pre-converter and the #1 O2 sensor is located in the exhaust manifold.
#6 is called Resonator and pipe ( not an cat converter )
As to your question:
The O2 sensor to check ,will be beyond the flex pipe.
And #4 is the cat you have to inspect

Well then,
You have twice as many chances then… :unsure:
But the O2 sensor you need to look at would be after your second cat.
If it turns out to be a faulty cat …..
You’ll need to do some testing then to determine which, if not both are defective.
Hopefully you get lucky with just a bad O2 sensor

Ok ..
First thing…
Clean and lubricate that assembly.
Way too much corrosion.

I tweaked one of your pics

You have to see that the back of the idle cam is resting on the tip of the adjustment screw when the engine is warm.
Looks like you have to remove the air intake off the throttle body and may need a mirror to get a good look.
I also see a wire loom directly under the linkage in your picture.
Make sure that it is not interfering with the idle cam movement.

is it advisable to touch the adjustment screw? You can but, I’ve yet to see one loosen up to where it affect the idle.
Also what did moved on the pics,,2 spring coils top and bottom,i called them spring coils but probably they are some kind of thermistor coils? Thank you
The top spring(which is just a spring) is part of the thermostatic control, the bottom spring is just that a tension spring.

I know it tough to explain without detailed pictures..
If this doesn’t make sense, my 3.3L V6 has a similar setup.
I can do a quick video if you need to show how the setup operates.

[quote=”Boyet” post=156049]Hi,so in order to clean it, i have to remove the trottle body assembly,correct? And what specific area that needs lubrication and what kind of lubricant? Thanks[/quote]
No, you can clean it up with out removing it.
Just spray it down with carb cleaner and use a brush to get the crust and rust off, then use a good lubricant on all the moving linkages and springs.
You can use pretty much any decent spray lube, WD 40, PB Blaster, even some clean motor oil will be better than nothing.