Hello, I am new to this site as well as a new owner to 2001 QX4. Bought it with known issues and don't ask me why but for some reason I am following in love with this car. Main issue is ECM causing high idle and surging idle intermittently. Has new idle control valve installed previous owner was told ECM needed to be repaired etc... I have several companies advertised but don't know if one is any better than another. I am in California so would prefer in state. Any recommendations from experience would be helpful. Thank you

Hi, and welcome, Johnlpg86!

I know exactly how you feel - I have replaced and repaired so many things on this car, and don't mind it one bit.

There is a plethora of info on this site and elsewhere regarding the ECM and IACV, as it is a known issue. Long story short, the IACV gasket fails, allowing coolant to enter the unit, which shorts out the ECU. The repair is pretty simple:

1. Find an eBay seller who will repair the ECU, around $100.
2. If the previous owner installed an aftermarket IACV, you WILL need a new OEM Hitachi unit. They are about $100 on Rockauto (part #ABV0043).
3. Install the repaired ECU and new IACV, then perform the idle relearn procedure. This takes some patience! Make sure to follow the FSM instructions to the T, including allowing the transmission to warm up for ten minutes of driving.

Thank you rgk
I have the original ECU installed as well as a used Hitachi one supplied by the seller. Of course the car wont even start with that one installed. Do you know if the used one can be done for my QX4? I ask so that way I can at least keep going to work.
Also they had replaced the IACV it is obviously new that is how they determined the issue with the ECU. Do you know if will I still need to replace the IACV?
I get concerned with problems I have no experience with and the same for companies that was why I was seeking some referral for one.
Regardless thank you very much for your time
John

I'm a little confused with your response, so I'll clarify, and maybe you can too.

When coolant enters the idle air control valve (IACV), it creates a short, which fries the electronic control unit (ECU), also known as the car's computer.

If you replace the IACV, but don't fix the ECU, you will continue having idle trouble.
If you fix the ECU, but don't fix the IACV, the bad IACV will once again short out the ECU.

The IACV can not be repaired, you have to replace it. The ECU can and should be repaired - it is far more economical than replacing it. I am not sure whether your IACV or ECU is bad, or both. Can you clarify?

The IACV is made by Hitachi; to my knowledge the ECU is not. I am a little confused when you said you have a used Hitachi ECU.

When I pulled the original ECU the first thing I did was compare it to the additional one the seller provided. Both labels read Nissan manufactured by Hitachi.
Seller's mechanic replaced IACV and told seller ECU would need repair. At least that is what I was told. It is obvious that the IACV is new.

Welcome to the board!

I see. I went with myairbags.com via eBay and they did a fantastic job.

https://www.myairbags.com/product-categ ... &year=2001