Help! Engine Problem

[Daniel]

Edit: Engine is KA24DE

Hey I always fill my 240 with 10w-30 castrol gtx the normal kind not high mileage with about 4.5 quarts. So lately it's been idling rough between 800-1000 and sometimes shaking. Maybe it was because it needed an oil change , it was about due for one anyways. So I take it to my mechanic because I didnt have time, this is the first time and I think they dont know my car better than me because after I got it back it was shaking even more. Now here are the symptoms:

Accelerates and Drives fine, but at a stop will idle rough shooting between 400-500 and up to 700-800 when the normal idle is at 1,000.

Occasionally, at least 3 times now after the car was driven for more than an hour will not start up on the first try, seems to take 5-6 seconds to catch the engine, will not start immediately at 1,000, starts at 400-500 then shoots up to 1,000 then after couple seconds starts idling roughly again.

So those are the symptoms:

1. DO i add oil?
2. Do I change the oil to the way I normally do?
3. Is it a completely different problem?
4. Note: My coolant was changed about a month ago by myself, could this be a problem? Coolant levels are fine.
5. For some reason, is the problem that my aftermarket cone air filter needs to be cleaned?
6. Any other problem?

Thanks in advance for all your help. This is the worst my car has been in the whole 3 years I have had it.

[Flybert]

Normal idle is around 800. I'm assuming you aren't throwing any codes.

Clean your AIV, clean IACV, clean your filter or replace it, check your plugs and maybe replace them.

[Daniel]

just a guess is AIV air intake valve? And what is the other thing iacv??

[Daniel]

where can i find this aiv and aicv??

[the head]

follow the small hose that branches off of your intake before the TB and runs to the manifold (prob about 1-1.5" dia) where ever that hooks up is where you idle air control valve (IACV or ACV) is located it is probably just gummed up with deposits

[Daniel]

what is TB?

[trixxxr4_kids]

you might have actually put to much oil in your car ,check the dipstick i
believe that your supposed to be at 3 & 7/8 qts , that was on 240sx.org a while ago they had posted a 240sx Info sheet that gave a great deal of OE equipment , or maybe its your MAF (air flow sensor by the airbox) because when you drive with no filter and your at idle it idles just like you say

[s13gonwild]

no fluids will cause your car to idle like that, or make your car act up THAT much unlesss you have 2 year old oil. and throwing 4 quarts in even has always worked for me.....spark plug gaping? new plugs needed,dirty injectors?

my car has always had a idle like that...jumps up and down from 900 to 600 to 700 and around there....its my #4 spark plug threading...the spark plug doesnt go in correctly...but i dont bitch about it..car runs fine other than that. itll go away after i drive for a while.