90' 240sx idle issue. ka24e

[abranovi]

Hey guys-
New here. Just picked up my 240 today.
It is a 1990 with 127k miles on it, and has been sitting for around a year.
On start up, i heard the lifters, this went away as the car ran for a while.
Now that I have been tinkering with it all day, I have noticed that it usually idles around 1250-1500rpms when warm. Sometimes, rarely, It will go back down to ~850.
Also, when it idles there, it is very steady and the car seems to be functioning totally normally. No weird surging or anything. It is just idling higher than it should.
I am totally new to 240's so I have no idea what to check, other than for vacuum leaks. Any other reason this might be happening?
thanks for any input!
-Ryan

[shiro_neko]

Well since you only had it today and dont know any history about it. I suggest you do some basic tune-ups first. change your oil, oil filter, spark plugs, air cleaner, timing etc... then start from there. Idle issues are really tricky. It has various causes and solutions. so make sure you cover the basics first before you dig in deeper.

[abranovi]

Well since you only had it today and dont know any history about it. I suggest you do some basic tune-ups first. change your oil, oil filter, spark plugs, air cleaner, timing etc... then start from there. Idle issues are really tricky. It has various causes and solutions. so make sure you cover the basics first before you dig in deeper.

Oil actually looks spotless, The plugs appear to have been changed very recently, Air filter is totally clean, no need to replace, and the timing chain isn't making noise. I probably will change the oil and do new plugs&wires just to be sure though.

[shiro_neko]

Any symptoms other than a high idle? any ECU codes?

[abranovi]

Not throwing any codes. no other symptoms. It is as if it is running totally fine, just at a higher idle. Sometimes though, it will idle at 850.

[shiro_neko]

oh darn my reply didnt post. anyway here's what to check:

ignition timing.

vacuum leaks.

throttle cable and throttle plate.

air regulator. pinch the hose with plers and cloth. air regulator should stay close when warm. if idle drops by pinching then it might be bad.

fuel pressure regulator. remove the vacuum hose and try to start. if it improves, check your fuel pressure.

thats it for now.

[abranovi]

Ah thankyou! that is super helpful. i will check all of those out asap.

[abranovi]

Another thing to note. Today when i ran it, it warmed up, was idling at 850 for a some time, and stayed that way when I moved it in my driveway. then, I drove it around the block a bit, gave it a little gas, and when I got back it was idling at 1500. IDK if that makes any difference, but maybe?

[shiro_neko]

is the temp gauge in the middle when its at 1500? the car is at its operating temp when its in the middle. and that would be your normal idle. pull out your ecu and check the ECU mode screw. if it has an idle adjust, turn it all the way to low.