1990 Nissan 240sx erratic idle problems-I need help!!!

[MOscapinski]

I have spent the last year trying to figure out this problem. I replaced the engine last year, I have also replaced almost every sensor on the engine but I still have and idle problem. The car starts up fine. Once it's warmed up, when I drive it and come to a stop, the idle will move up and down for about 5 to 6 times from 500 to 800 rpms, then it stabilizes. I have a new exhaust system with a header and a throttlebody spacer. Every machanic I have taken my car to says they can't figure it out. All they say is that it's probably the upgrades on my car but this problem has been occuring before the upgrades. I have replaced the EGR valve, O2 sensor, the fuel injectors, the throttle body has been cleaned, 2 selinoids, the fuel filter, rotor, cap, plugs, and wires, also. I also tried a used AIC valve too but the same thing occurs. Any suggestions?

[madmeg323]

I had the same problem ( no swap though) . So let me guess you can walk out side and crank it and it will idle fine all day. You can take off and go down the road and it will run fine until you come to a light and stop, it will cough and choke and die, if you hit the throttle it will even out and idle fine until the next light. Correct???

If so your answer is Vacuum Leak, Not my credit...SRpowered240sx helped me out



Check all your hoses....ALL OF THEM

[homeslicej2]

I had the same problem ( no swap though) . So let me guess you can walk out side and crank it and it will idle fine all day. You can take off and go down the road and it will run fine until you come to a light and stop, it will cough and choke and die, if you hit the throttle it will even out and idle fine until the next light. Correct???

If so your answer is Vacuum Leak, Not my credit...SRpowered240sx helped me out



Check all your hoses....ALL OF THEM

And if that is not the case (it should be though) the other thing that comes to my mind is you might have grounding issues, but that usually affects it all the time. Still something to consider if it's not a vacuum leak, but I think it's vacuum too.

[xpicer]

try to get your hands on a smoke machine. atach it to a intake port and check for smoke coming from a place it shoudnt maybe intake gasket hoses Etc.. GOOD LUCK

[MOscapinski]

The car won't die when I stop, the idle just will fluculate up and down, up and down. I had a smoke test done on the vaccum leaks. There were some. I fixed them but it still idles rough.

[Accord-240sx]

if you already checked your vaccum lines. It could be air in your antifreeze making it idle weird when it gets hot. Bleed your antifreeze or blurp it (let the air out) then add more antifreeze. I have never done it on a 240 but I did it on my accord.

The other think I can think of is your IAC valve ( Idle Air Control) is bad and needs to be replaced.

[homeslicej2]

...The other think I can think of is your IAC valve ( Idle Air Control) is bad and needs to be replaced.

This sounds like a good candidate as well.

[MOscapinski]

How and where do I bleed the anti-freeze? I also checked the ecu for error codes today and there were none. I recently changed out the aacv and it did not change anything.

[Accord-240sx]

I said the IAC valve not the AACV. The IAC if its bad it will not throw out a code. My guess its the IAC valve. I dont know how to bleed the antifreeze on the 240 cause I never done it on the 240 only on the accord so I couldn't help you on that one.

I hope this helps

[240sxka-t]

turn the heater on before to open the system theres a bleeder on the bottom of the radiator. do that and remove the cap and it will drain. . and then remove the bottom hose to drain it more.

thats about it. then run it and add more.

[DrJuice164]

Not sure thats the proper way to bleed the system. From my understanding,

1. you jack the front of the car up 6 inches or however much so that the top of the rad is the highest point (so the air flows there).

2. Open the bleeder screw that is on your intake mani, make sure not to lose the copper washer.

3. Fill as much coolant you can, but the heater on hot and then start the car.

4. Keep filling the rad cap until there is a good stream coming out from the bleeder screw, then put the screw back in, (careful area will be hot).

5. Continue running the car/filling rad until full. Then fill the overflow.

Please correct me if this information is incorrect.

PS, when my car had overheating issues, the RPM's would just raise to constant 1000-1100 rpm, there was zero fluxuation.

[shinjitsu]

did you ever find the problem i have the same problem