cherishzm

I have a '95 240SX with 145,000 miles on it. When I almost got to work this morning, check engine light came up and it's still there.

After it happened, my car doesn't seem be in normal condition. The first thing that I noticed was unstable idle. When it was normal, idle RPM used to be around 600~700 with A/C off, but now sometimes it idles at around 1100~1200 and sometimes goes back to normal. Also it seems to hesitate while shifting and does not drive smoothly.

I bought it from my friend and it was not really maintained except oil change.

What could possibly cause this problem? I don't feel comfortable driving it until getting it fixed. Your help will be appreciated.

Thank you.

mbui00

an unstable idle huh? ....it might be the aiv unit, that has been known to clog up with gunk and cause irratic idling problems. Thats one thing i can think of, if you say the only cleanup and maintenence ever done were oil changes. Thats my two cents.

mbui00

Hmm, also check the maf sensor to see if there is buildup as well

cherishzm

Thanks for your replies, mbui00. I went to my mechanic today and he said he needs more time to figure out what's wrong.

After I got home, I did some research and found ECU trouble codes on KA24DEvelopment.com website. So I decided to try to read a trouble code by myself today.

BTW,
"AIV" = Idle Air Control Valve,
"MAF sensor" = Mass Air Flow Meter Sensor

Right? Where is the MAF sensor located?

Today, my 240SX stalled three times while making turns and I noticed extremely low RPM (idles around 100~200 RPM with A/C off, 500 RPM with A/C on).

I appreciate your help.

mbui00

the maf sensor is right next to the stock intake box its connected to the intake piping and has wires coming from it.

the aiv unit is located just north of the stock intake box and maf, kinda looks like a lil black box.

hopefully the mechanic will find out whats wrong

that is some lowwww idle lol

I think there are threads either on nico or here about how to disassemble and clean the aiv unit and also how to clean out the maf sensor if you happen to find gunk in there.

cherishzm

Finally I got the trouble codes from ECU diagnosis.

Code # 34 - Detonation (Knock) Sensor
43 - Throttle Position Sensor

Do I need to replace those parts or just clean? How hard is it to do that?

Thanks again for your input.

mbui00

its better if you replace the knock sensor, but those things are usually not cheap..unless you get one from the junkyard.

For the throttle position sensor, if that sensor is wacked out, then the computer ecu will not know how much fuel to deliver when you press down the throttle and let go. I'm guessing the throttle plate or whatever is connected to that throttle sensor, and when you press down the throttle, the plate will open and contact and give a volt signal to the throttle sensor. If it's bad, that might be the reason why you get such a unstable idle and random stalls cuz the ecu is just like randomly spurting fuel thru injectors (might be cause for the stalls) when your turning and whatnot, i guess you let go off the throttle going into a turn?

Either way, you can try getting those sensors and replacing them, and see if that will work.

mbui00

I hope that helps

People usually tell me im wrong when i try to solve a car problem, but you know..im just a noob tech ...i work at ntb as a general service but i have been taking some auto classes such as auto electricity and auto electricity II (kinda barely passed it though )

cherishzm

All right. I'll try to get those sensors replaced soon. BTW, is there any place on the web to buy them cheaper? (I went to NAPA and TPS costs $45 and knock sensor costs $169.)

Thanks a lot again, mbui00.

mbui00

hmmm im not sure but someone else might if they read this thread. 169 dollars seems a lil too much for me.