Question about 1993 Nissan 300ZX

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High idle; 1500-2000 rpm; suspect idle control module?

Heard that they can be removed and cleaned but is it a practicle solution or should replace. Also heard that leaking fuel injector seals can create similar problem and even more costly to fix?

Problem existed when i got the car @ 125K miles. Did timing belt kit due to no history on the car. Installed cam angle sensor. Not sure how to set ignition timing. I am sure there are several things to the procedure. No manuals available. I did pay $50 for a wiring schematic. 10% of the color/stripe codes were in corrrect.

Thanks... Chuck H.

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First I would look for a vaccum leak. Many times a high idle can be the result of this. Just listen for a hissing sound while the engine is running. Sometime it may even be a cracked vaccum line and you can't hear hissing. Use some WD-40 or carb cleaner and spray around the suspected area or hose. If the engine slows down for a minute when you spray you've found the leak.

Posted on Feb 09, 2009

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Posted on Jan 02, 2017

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1 Answer

Correct code P0504?


What Colorado do you have ? 2 wheel or 4 wheel drive ? Sport ,sport LS 3.5L , Z71, Z71 LS. etc. what size engine ? an does it have electronic throttle control ? I have factory service info an it is not showing that code .
DTC P0506

Circuit Description

The throttle actuator control (TAC) motor is controlled by the powertrain control module (PCM). The DC motor located in the throttle body drives the throttle plate. In order to decrease idle speed, the PCM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the PCM commands the throttle plate open allowing more air to pass the throttle plate. If the actual idle RPM does not match the desired idle RPM within a calibrated time, this DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:
DTC P0506 Idle Speed Low
DTC P0507

Circuit Description

The throttle actuator control (TAC) motor is controlled by the powertrain control module (PCM). The DC motor located in the throttle body drives the throttle plate. In order to decrease idle speed, the PCM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the PCM commands the throttle plate open allowing more air to pass the throttle plate. If the actual idle RPM does not match the desired idle RPM within a calibrated time, this DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:
DTC P0507 Idle Speed High
Cleaning the throttle body mite take care of it !
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Jan 31, 2015 | 2005 Chevrolet Colorado

1 Answer

Idle to high


There is, most likely a vacuum leak somewhere that is causing the high idle. Or the idle air control valve is malfunctioning. Some can be removed and cleaned, others may need to be replaced.

Apr 22, 2014 | 2005 Toyota Avensis 2.0

1 Answer

Code p1506


P1506 - Idle Air Control (IAC) Overspeed Error This DTC is set when the PCM detects engine idle speed that is greater than the desired rpm.
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Hi, my rpm stays on high after cleaning the idle control valve


An IAC (idle air control) motor is designed to adjust the engine idle RPM speed by opening and closing an air bypass passage inside the throttle body. The cars computer or ECM (electronic control module) receives information from various sensors and will output signals to adjust the IAC motor in or out to adjust engine idle speed by controlling engine idle air. ----------------------------------------------------------------------------------------
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3 Answers

When my car is idling or I come to a stop it is chugging, when I accelerate it is fine. The RPM's drop to just under 1000. This just started, I thought maybe bad gas, but filled up with High Octane gas...


Could be a variety of systems, however I would suggest the following first:
Don't waste money on High Octane fuel or injector cleaners. These have very little to no impact on performance anyway.

Idle Air Bypass or Idle Air Control Valve.
You can often test this while at idle with AC off. Then turn AC on to determine if the RPM or idle changes. If no, then suspect the IAC valve.
It can be bad or just be very dirty (ports blocked).
Remove, clean and replace to see if that helps. If you see a lot of carbon buildup, then get that all cleaned up.
If this does not help, then replace with a new one and go from there.

Let us know, then we will try something else.

Jan 10, 2018 | Pontiac Grand Prix Cars & Trucks

1 Answer

High --1600 rpm ?? rpm idle


The normal idle speed is below 1,000 rpm...between 800 to 900 rpm. I suspect that the idle-air control motor has seized and can no longer automatically adjust the engine's idle speed. This part is also responsible for slightly increasing idle speed when the airconditioning is switched on to compensate for the added engine load. Some cars even have a "step-up" solenoid to increase idle.

When replacing the idle-air control motor, remember to clean the port that IAC motor goes into; there will be some carbon build-up that may prevent the part's cone-shaped valve from seating properly. A can of intake valve spray helped along with some Q-tips works well.



Hope this helped.

Have a great day !!!

Apr 07, 2011 | 1992 Buick LeSabre

3 Answers

My 2005 altima idles high and engine code


This P0507 code is one that's sometimes triggered on vehicles that have electronic throttle control. That is, they don't have a regular throttle cable from the accelerator pedal to the engine. They rely on sensors and electronics to control the throttle. In this case, the P0507 DTC (diagnostic trouble code) is triggered when the PCM (powertrain control module) detects an engine idle speed that is greater than the desired (pre-programmed) RPM. In the case of GM vehicles (and possibly others) if the idle speed is over 200 rpm higher than expected, this code will be set.

Jun 07, 2010 | 2005 Nissan Altima

1 Answer

Will idle high sometimes up to 3000 rpms when driving or sitting still


I have the same Jeep and same problem. The engine was running rough. The Jeep dealer fixed a vacum problem in the manifold and they then decarbonized and cleaned the fuel injectors. After these repairs the idle problem began, it would spike to 2000 rpm while sitting at idle, sometimes it would slowly come down, sometimes I would have to tap the accelerator. I took it back in and they then replaced the throttle motor and reprogrammed the PCM (Power Control Module?) Still same problem. Now they suspect a another vacuum leak and I am taking it back in on Tuesday, will let you know what happens, $ 1,300 so far.

Jun 02, 2009 | 1999 Jeep Wrangler

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