I am still suffering from 97 Nissan Pathfinder idling issues - I changed the spark plugs as they were filled with carbon really bad!
I swap that out, changed the EGR valve as well, and the car ran to idle fine. The accelerator linkage did break and it was replaced.
Now what I see is the engine losing RPM - 300/380 vs 800 when I changed the spark plugs. Now today, raw fuel burning, black spot in the side walk.
I am throwing in the towel not knowing what else it can be, can someone chime in to see what else it is.

You're doing the right things by fixing all those issues because they all work together to operate the engine properly. The root cause of the issue may have multiple contributing factors so getting the basics in good working order will help you resolve the problem. The engine controls rely on several basic elements that are manually adjusted. Start by getting these all corrected as necessary. The Nissan factory service manual, engine control section, page 25-29, is a good place to start. https://www.nicoclub.com/service-manual ... 7%2Fec.pdf Checking the fuel system pressure, fast idle cam inspection and adjustment, and idle speed/ignition timing/idle mixture ratio adjustment are all things expected to be correct and needing correction on these older Pathfinders. Study this section of the service manual. You are already doing things that need to be done so if you can help it, don't throw in the towel just yet.

mdmellott wrote: ↑

Tue May 16, 2023 7:17 am

You're doing the right things by fixing all those issues because they all work together to operate the engine properly. The root cause of the issue may have multiple contributing factors so getting the basics in good working order will help you resolve the problem. The engine controls rely on several basic elements that are manually adjusted. Start by getting these all corrected as necessary. The Nissan factory service manual, engine control section, page 25-29, is a good place to start. https://www.nicoclub.com/service-manual ... 7%2Fec.pdf Checking the fuel system pressure, fast idle cam inspection and adjustment, and idle speed/ignition timing/idle mixture ratio adjustment are all things expected to be correct and needing correction on these older Pathfinders. Study this section of the service manual. You are already doing things that need to be done so if you can help it, don't throw in the towel just yet.

Thank you for the inspiration, plug the OBD-2 again and notice the oxygen sensor monitor blinking Red.
Everything running how it suppose to, it idle fine until it was warming up so the only factor is that O2 Bank 2 sensor 2 was read a few months ago. Then it reset itself again, just the monitors were blinking now. I have to order the Bosch on Rockauto, Nissan Parts want $198/each.

Keep in mind what the O2 sensors do. I like to think about them as witnesses to events that have occurred upstream. They do nothing on their own. They only give testimony as they see it and then your PCM decides what to do with that information. O2 sensor 2 on both banks are unique in that no matter what they say, the PCM does nothing with the information other than flag it has faulty or with some other DTC pointing to catalytic converter issues. Those two downstream O2 sensors have absolutely no influence on the engine controls. Vehicles would function perfectly normal without them. They are only for emissions control purposes or as I have heard one Nissan technician put it, "sensor 1 is for the engine and sensor 2 is for the government."

If that sensor 2 is bad it should be replaced but it will make no difference in how your engine is currently performing. I bought Bosch O2 sensors for my Pathfinder as well. They are very reliable witnesses.

mdmellott wrote: ↑

Tue May 16, 2023 7:25 pm

Keep in mind what the O2 sensors do. I like to think about them as witnesses to events that have occurred upstream. They do nothing on their own. They only give testimony as they see it and then your PCM decides what to do with that information. O2 sensor 2 on both banks are unique in that no matter what they say, the PCM does nothing with the information other than flag it has faulty or with some other DTC pointing to catalytic converter issues. Those two downstream O2 sensors have absolutely no influence on the engine controls. Vehicles would function perfectly normal without them. They are only for emissions control purposes or as I have heard one Nissan technician put it, "sensor 1 is for the engine and sensor 2 is for the government."

If that sensor 2 is bad it should be replaced but it will make no difference in how your engine is currently performing. I bought Bosch O2 sensors for my Pathfinder as well. They are very reliable witnesses.

That is my last resort before testifying amongst the judge. I located all 4 so might as change them all.

I finally switched all 4 sensors, it ran great until getting into work - the car starts to stop idle from 800 - 350 rpm. Just waiting on the EGR control valve hose to come in to see if that's the final missing puzzle that I need to complete.

jetstream87 wrote: ↑

Fri May 26, 2023 5:11 pm

I finally switched all 4 sensors, it ran great until getting into work - the car starts to stop idle from 800 - 350 rpm. Just waiting on the EGR control valve hose to come in to see if that's the final missing puzzle that I need to complete.

Curious to see what the ultimate culprit is/was or if it was several factors coming together.

palmerwmd wrote: ↑

Mon May 29, 2023 5:14 pm

jetstream87 wrote: ↑

Fri May 26, 2023 5:11 pm

I finally switched all 4 sensors, it ran great until getting into work - the car starts to stop idle from 800 - 350 rpm. Just waiting on the EGR control valve hose to come in to see if that's the final missing puzzle that I need to complete.

Curious to see what the ultimate culprit is/was or if it was several factors coming together.

Alright - so the car idles fine at times, today I pump some 91 fuel, added a lucas treatment. So this is what I have done to the car so far:
1. Changed the EGR valve
2. Spark Plugs (5/6 were filled with carbon, Blacker than my sins and soul)
3. Cleaned the Intake manifold.
4. Changed all 4 (o2) sensors with Bosch, since they were carbon build up on all 4 as well.

Some odd reason I decided to drive with the OB2 - plugged into the car since I have the monitors to set (O2, EGR, EVAP, and CAT [ this one is out the window, I need to replace them. It is $1,200 last I check to replace both. I am sure its much more now since CA is the theft capital of catalytic.]). Came to realize the code P0505 (Pending) shot up in the OB2. The part at Nissandealparts is $500 vs generic is about $130 - $300 give or take if I remember correctly. I have never changed this part or cleaned it, will it be better to clean it and see the miracle it will be fixed or swap the part (generic or OEM)? I cannot seem to locate the I.A.C. at all since I tried peeking through the car. I saw the diagram and it should be in the driver side back of the engine???? How can I get access to this? I have never removed the top part of the engine myself before due to the fear oooopppsss forgot this hose, forgot to connect this wire, or simply Sh*t the gasket is all crooked because I did not tied the bolts to its proper pattern.

I stand by my first post on this. "The Nissan factory service manual, engine control section, page 25-29, is a good place to start. https://www.nicoclub.com/service-manual ... 7%2Fec.pdf Checking the fuel system pressure, fast idle cam inspection and adjustment, and idle speed/ignition timing/idle mixture ratio adjustment are all things expected to be correct and needing correction on these older Pathfinders."

Don't throw any money at this until you have checked and adjusted fast idle cam inspection and adjustment and idle speed/ignition timing/idle mixture ratio adjustment. These are basics that need to be correct. If they are not, you will never get the idle issue corrected. It is possible you have nothing more than out of specification adjustments that need to be made.

Given the P0505 code you see, regarding your IACV, I suggest looking at pages EC-337 through EC-340 as well. Even if you find, through this inspection of the IACV, that the IACV needs to be replaced, the basic idle adjustments still need to be correct or else you will continue to have idle issues.

mdmellott wrote: ↑

Mon May 29, 2023 8:33 pm

I stand by my first post on this. "The Nissan factory service manual, engine control section, page 25-29, is a good place to start. https://www.nicoclub.com/service-manual ... 7%2Fec.pdf Checking the fuel system pressure, fast idle cam inspection and adjustment, and idle speed/ignition timing/idle mixture ratio adjustment are all things expected to be correct and needing correction on these older Pathfinders."

Don't throw any money at this until you have checked and adjusted fast idle cam inspection and adjustment and idle speed/ignition timing/idle mixture ratio adjustment. These are basics that need to be correct. If they are not, you will never get the idle issue corrected. It is possible you have nothing more than out of specification adjustments that need to be made.

Given the P0505 code you see, regarding your IACV, I suggest looking at pages EC-337 through EC-340 as well. Even if you find, through this inspection of the IACV, that the IACV needs to be replaced, the basic idle adjustments still need to be correct or else you will continue to have idle issues.

Bam! confirmed the MIL came on today and threw the P0505 code, not sure why I over looked the IACV to clean it in the beginning. I have never cleaned it or have changed it I owned the car since 125K miles and not it has 212K miles. The OBD-2 picked up the code right away, as soon I parked the car in the grocery store parking lot the car shut off right away. I was able to get it back home after getting some groceries, however the lights dimmed when parking, and started to smell raw fuel unburnt.

How can I get access to this unit to look into it so I can at least clean it and hope it is that easy. I do have a spare gasket in hand to replace (new). I want to take a look at this unit and give it a clean. While I am there what do I need to look for when this is bad? Any section where I can look how to remove the top plenum, going to try to work it with my dad. Just want to see the torq specs and the pattern to bolt to ensure the gasket does not end up crooked.

I don't think you need to remove your intake plenum to get at the IACV. I grabbed a couple of images of the IACV on your "97 Pathfinder to give you an idea where to look. These are poor images for any detail but they should help you find it. The engine controls section of the factory service manual is going to tell you everything you need to do to test it and confirm that needs replacing or not. It's worth taking a look at but take care of all the basics I have mentioned so you are not chasing after the wrong things. https://www.nicoclub.com/service-manual ... 7%2Fec.pdf