Fluctuating RPM's

Hi,

First, I have to explain this vehicle isn't offered in the US so my technical information is extremely limited. However, I will try my best to help.

What you described sounds like a bad idle air control valve (IAC). The IAC is responsible for maintaining the engine idle speed. Take a look through these two links that explain how to service the idle control valve and one that explains in general how one is replaced.

https://www.2carpros.com/articles/idle-air-control-valve-service

https://www.2carpros.com/articles/how-to-replace-an-idle-speed-control-motor-iac

You can try to service the one on your vehicle, but before you replace it, I would suggest checking for engine vacuum leaks. A vacuum leak can cause idle issues as well.

Here is a link that explains how to check for a vacuum leak. You should do this as well before replacing parts.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know if this helps. If you have other questions, feel free to let me know. Although there many different brands and models, the all work primarily the same.

Take care,
Joe

Hi,

I didn't realize it did it while driving. I thought it was at idle. When the engine is revving up and down while driving, do you feel the vehicle accelerate and decelerate?

Let me know. Also, has the check engine light come on and stayed on with the engine running?

Let me know.

Joe

I suspect it is one of the first things I mentioned. However, before we start replacing parts, I strongly recommend having the computer scanned for diagnostic trouble codes. If the engine light is staying on, there are codes stored in the computer that will help direct us to the problem.

Here is a quick video that shows how it is done:

https://youtu.be/YV3TRZwer8k

I realize most people don't own a scanner, but most parts stores will do it for free or lend/rent a scanner to you. Have this done and that way I'll have a better idea as to which way to direct you.

I will watch for your reply.

Take care,
Joe

Hi,

That is possible. Do you know what the codes are that were found? Usually both don't go bad at the same time, but anything is possible.

Here is a link that shows in general how to replace cam sensors. It really isn't hard, and if you do it, you'll save a lot of money. The parts shouldn't be that expensive. However, I don't recommend getting a really inexpensive one online. Get something with a brand name that people recognize. I can't tell you how often people get things offline really cheap and either they don't work or they don't work properly.

https://www.2carpros.com/articles/camshaft-angle-sensor-replacement

Please feel free to let me know if I can help or if you have other questions.

Take care,

Joe

That is the throttle position sensor. Yes, it could cause the issue. Did the dealer check it to confirm it is bad before you just replace it? I'm sure it isn't an inexpensive part.

Let me know.

Joe

Hi,

There are test procedures, but I don't have the specifics on this vehicle because it isn't offered in the US. I can provide a general test for a different model Nissan, such as a Sentra. But that has a 1.8L engine.

Let me know.
Joe

Here are the directions I have for an 02 Sentra with a 1.8L. The attached pics correlate with the directions.

_________________________________________-

2002 Nissan-Datsun Sentra GXE L4-1.8L (QG18DE)
Component Tests and General Diagnostics
Vehicle Powertrain Management Fuel Delivery and Air Induction Sensors and Switches - Fuel Delivery and Air Induction Throttle Position Sensor Testing and Inspection Component Tests and General Diagnostics
COMPONENT TESTS AND GENERAL DIAGNOSTICS
Component Inspection

THROTTLE POSITION SENSOR

With CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Stop engine (ignition switch OFF).
3. Remove the vacuum hose connected to the throttle opener.

Pic 1

4. Connect suitable vacuum hose to the vacuum pump and the opener.
5. Apply vacuum [more than -40.0 kPa (-300 mmHg, -11.81 inHg)] until the throttle drum becomes free from the rod of the throttle opener.
6. Turn ignition switch ON.

Pic 2

7. Select "DATA MONITOR" mode with CONSULT-II.

Pic 3

8. Check voltage of "THRTL POS SEN" under the given conditions.

NOTE: Voltage measurement must be made with throttle position sensor installed in vehicle.

If NG, adjust closed throttle position switch. Refer to "Basic Inspection".

9. If it is impossible to adjust closed throttle position switch in "Basic Inspection", replace throttle position sensor.

Without CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Stop engine (ignition switch OFF).
3. Remove the vacuum hose connected to the throttle opener.

Pic 4

4. Connect suitable vacuum hose to the vacuum pump and the opener.
5. Apply vacuum [more than -40.0 kPa (-300 mmHg, -11.81 inHg)] until the throttle drum becomes free from the rod of the throttle opener.
6. Turn ignition switch ON.

Pic 5t

pic 6

7. Check voltage between ECM terminal 92 (Throttle position sensor signal) and ground under the given conditions.

NOTE: Voltage measurement must be made with throttle position sensor installed in vehicle.

If NG, adjust closed throttle position switch. Refer to "Basic Inspection".

8. If it is impossible to adjust closed throttle position switch in "Basic Inspection", replace throttle position sensor.

_______________________________

I don't know if you vehicle will be similar. Let me know.

Joe

Hi,

Nothing should be loose. However, hold the throttle plate when you shake it to see if that stops the noise.

Next, I believe where you pointed is where the idle air control valve (IAC) allows air to enter the engine when the throttle plate is closed. Have you removed the IAC and inspected it?

Let me know.
Joe