Pathfinder rough idle/surging

[savePF]

MmI have a 93' Pathfinder 

V6 automatic. It has a rough idle and engine surge.

It usually starts right up, idles up to 900 rpm, then drops to 4-600 and idles rough.

 

It also has a slight stumble in park during acceleration. Check engine light on.

 

Here is what I have done so far.

REPLACED-

Burned out ECU (no codes)

Air filter 

Plugs

Distributor cap

Rotor

EGR and hose

PCV valve

Coolant temp sensor

Battery

 

CLEANED-

MAF

Throttle body(front and back)

Entire engine bay

 

CHECKED-

O2 sensor by unplugging while running

All vacuum hoses

And replaced any worn, cracked.

 

Did the carb cleaner vac hose spray test on all visible (including the slightly hidden FPR) vacuum hoses.

 

The only thing I can think of is the IAC?

 

Please help!

 

Thanks

 

 

 

 

 

 

 

 

[savePF]

4 hours ago, savePF said:

MmI have a 93' Pathfinder 

V6 automatic. It has a rough idle and engine surge.

It usually starts right up, idles up to 900 rpm, then drops to 4-600 and idles rough.

 

It also has a slight stumble in park during acceleration. Check engine light on.

 

Here is what I have done so far.

REPLACED-

Burned out ECU (no codes)

Air filter 

Plugs

Distributor cap

Rotor

EGR and hose

PCV valve

Coolant temp sensor

Battery

 

CLEANED-

MAF

Throttle body(front and back)

Entire engine bay

 

CHECKED-

O2 sensor by unplugging while running

All vacuum hoses

And replaced any worn, cracked.

 

Did the carb cleaner vac hose spray test on all visible (including the slightly hidden FPR) vacuum hoses.

 

The only thing I can think of is the IAC?

 

Please help!

 

Thanks

 

 

 

 

 

 

 

 

I see this has been read a little. If you can please post whatever you have.

Thank you

[adamzan]

The engine light is on? What are the codes it is reporting?

[savePF]

2 hours ago, adamzan said:

The engine light is on? What are the codes it is reporting?

No codes

[savePF]

22 hours ago, savePF said:

No codes

Any help out there?

[FirstGenFreak]

Try a good IAC, then maybe do a smoke test for vacuum leaks. 
Check Grounds and elec connectors. 

 

All that being good I'd do a compression and leak down test to rule out rings or valves. 

Edited April 11, 2025 by FirstGenFreak

[savePF]

16 minutes ago, FirstGenFreak said:

Try a good IAC, then maybe do a smoke test for vacuum leaks. 
Check Grounds and elec connectors. 

 

All that being good I'd do a compression and leak down test to rule out rings or valves. 

Thank you very much

[savePF]

22 hours ago, savePF said:

Thank you very much

Does The IAC operate only during the idle cycle or both idle and higher speed?

I suppose if it were stuck in the open or closed position from carbon build up it would effect it during either cycle.

[savePF]

On 4/11/2025 at 5:37 PM, savePF said:

Does The IAC operate only during the idle cycle or both idle and higher speed?

I suppose if it were stuck in the open or closed position from carbon build up it would effect it during either cycle.

So I have tried everything  that you all have been nice enough to take the time to suggest.

 

Dropping at the mechanic on Monday.

I will let you all know what he finds.

 

Thank you again

[FirstGenFreak]

Best of luck!

[savePF]

So,

After all of the work and parts replacement, cleaning, diagnosing it turns out that my catalytic converter is bad!

It was blocking the exhaust which was the cause of all the symptoms .

Having it replaced.

 

The up side of all of this is that I really have learned a lot about my Pathfinder and had the opportunity to interact with and receive help from all of you folks.

 

It certainly won't be the last time you hear me chime in here.

 

Thank you