idle problem that wont go away

[nathanmoris]

Hi i have a 1990 240sx ka24e. I have tried to solve my problem with some trouble shooting i found in these forms but its not working. My car idles at about 1300. When i come to a stop its drops down to 800 rpm but once it settles, it rises to 1300. same thing when i start. starts low but then rises. I have replaced the injectors, and connectors, temp sensor, and connectors, changed the o2, checked the ohm on the air regulator and is where its supposed to be, changed out the tps sensor, changed out the fuel filter. I tried to adjust the idle manuel but it will only rise and and lower at all. The car was sitting for about 2 years prior to me getting it to run again. All was fine before it broke down. If anyone can help me out that would be great thanks for the help

[vancouverbc]

fully warm up the car and then squeeze the hose shut that goes to air regulator. it should have no effect on idle. it might be stuck open.

you might want to replace the idle air control valve. ive seen them for $100 new.

[ScrapMetal]

Try cleaning your MAFS.

[fuse=--action]

^What he said.

I had a similar problem, except in reverse. When I sat for a minute my car would bog at idle and want to die.

If neither of the above fixes work, there is a valve that allows air in at idle. I've heard that thing can make a big difference in your idle. May want to look at that.-fuse.

[Rucca]

your IAC (idle air control valve) is probably all gummed up. there is a post on here on how to clean it out. also you probably have a vacuum leak if not multiple vacuum leaks. spray down your intake manifold where it mates with the head with throttle body cleaner while hte car is running and see if your engine revs up. if you can spray anywhere along your intake or manifold and your engine revs up, you have an air leak there.

replace intake manifold gaskets and clean IAC while the manifold is out of the car. should fix it.

[Shift__BODOM]

It would be a GOOD idea to check the bundled rat's nest of vacuum lines behind the head. I tried to hunt down the exact same problem, and got so fed up with it that I ended up pulling the intake manifold. Turns out I had a broken fitting for my EGR/canister solenoid valve (ditched it all), and a couple of hoses with decent sized cracks in them. It'd be a really good idea to pull off the hood and climb up to a spot where you can look straight down into the crevasse behind the head. Get a bright flashlight and check every single one. Feel every line and if you feel even as much as a hairline crack, replace it.

If all the lines are O.K., you may have a break in one of your PCV hoses that connect to the intake runners. Pray it's one of the small lines behind the head because the PCV lines are hell to replace. Of course, this is all assuming that you have a vacuum leak. Exhaust every possible option before you go ripping stuff out (like the intake mani). Check the FSM (linked below) if you don't have one, and go through every single possible diagnostic process for high idle. Don't forget to check all the stupidly simple things first. Timing, idle screw (sounds like you already checked that one), clean the MAF (would probably cause a crappy idle, but not sure if it would cause a high idle).

http://www.bumnah.com/fsms/

Good luck, man.
Modified by Shift__BODOM at 4:49 PM 4/7/2008