Ive got a 90 240sx SOHC my car idles high 1400rpm, ive tried cleaning iaa unit, adjusting idle screw with tps disconnected, the ignition timing is 100% on point. i can warm car up and block off tube under the throttle body going to air regulator and iacv and hole on plastic intake tube and the idle lowers to about 1000-1200. other than this problem the car runs and drives great with lots of power. another factor is with all air hoses properly connected i can also disconnect the two harness plugs going to the two valves and their is no change in idle. ive checked the signal back to the ecu and the grounds for both connectors everything is 100%. my question is which valve seems to be at fault and what are other things that could lead to this high idle problem, the fsm call for a 750rpm idle..i would just leave it but i cannot pass smog with the car idling like this
Yes, a defective IAC valve can cause an incorrect idle issue. The other reasons or possibilities are: kinked or damaged throttle linkage, improperly adjusted idle screw, defective, loose, or improperly adjusted TPS sensor, vacuum leak, leaking base gasket (carb.), or the timing is off (maybe the distributor has been adjusted or is loose). I hope these suggestions help. Please let me know how your repair goes of if you have other questions, good luck.
Testimonial: "so i replaced the iacv with one off a different motor that was running perfectly and it made no difference, when the car warms up the idle jumps up to about 1400-1500"
prior to warming up the idle sits at 1200
Thank you for writing back with the update. I'm sorry that the IAC didn't do the trick. Would of been nice but I guess this one will take more time. I have another thought. Since you have another 240SX, would you please take a look at the way the "Fast Idle Valve" performs? If the valve, linkage, or cam is sticking then the engine will not be able to idle correctly. I can not help but to wonder if you are correct about the timing. I mean not to affend you. Maybe you do have it spot on. I guess I'm curious to hear if you played with the distributor? Fine tuning the timing can sometimes help. But if it makes no difference, then no harm done. My last idea has to do with the air/fuel mixture. Have you looked into how lean or rich the engine is running while this high idle speed occurs? That is all I have for now but write back soon. I'd like to hear how the repair is going, thank you and good luck.
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