97 Pathfinder idle hesitation/loss of power

[Merrix]

Happy St. Patrick's day!

I've been skimming through this forum page for a couple years now and finally decided to join the page.

Little bit of a backstory to help describe my issue: I bought my pathfinder just over 2 years ago and it has been great until about a year ago when I started chasing my issue. First thing that happened was a dancing speedo needle. Didn't think much of it for a few weeks till it finally stopped working and of course gave me a code. Finally looked into it and remachined the gear at the T case. When the speedo wasn't working is when I noticed a loss of power between 2k RPM and 3k RPM, most likely paranoia. I've replaced plugs, wires, distributor, fuel filter, cleaned and tested MAF sensor. This had helped a bit with performance but didn't resolve my symptom. At some point around this time I had a code for a crankshaft position sensor so I replaced that. Car drove fine but still with loss of power between 2k and 3k.

Out of the blue, I started getting a very rough idle and blue/white smoke out the tail pipe once the engine was warm but it would go away. The rough idle started happening more often and at times would stall. No codes every came up. After some research I decided to replace the 2 front 02 sensors which helped but than started getting codes intermittently for both sensors but never had performance issues. Most likely due to cheap sensors. I had tested my fuel pressure as well as regulator and both checked out. I pulled the plug and replaced the pump anyway. Still having the same issues. One morning on my way to work, the engine decided to die like the key was switched off. Got a P1320 code. Had an issue starting my engine but once I did, she ran fine. That code had came up 2 more times and one being just yesterday morning after doing a 100 mile trip the night before. Took a little bit to get her fired up but once she did, she ran fine.

I have many years of experience as a mechanic and I am completely stumped with this. Wish I still had access to those diagnostic machines. The codes I have had since I've owned the car have been for both front 02 sensors, MAF, P1320, usual knock sensor, CPS and speedo. The codes that keep coming up are 02 sensors (which I plan to replace next week), MAF which has been cleaned and tested ok and knock sensor. Next week I plan on replacing the cheap 02 sensors and putting my old distributor back in to see if anything changes.

If anybody cane shine some light on this, I would be extremely grateful. These issues have been limiting my driving adventures which has been quite the buzzkill and I got that whole pesky California smog coming up in May

Thank you!

[MisterH]

Perhaps your replacement distributor you purchased is defective. As you know, the camshaft sensor is built into that unit.

[Merrix]

Perhaps your replacement distributor you purchased is defective. As you know, the camshaft sensor is built into that unit.

I peeked inside the distributor cap to see it's condition and check for anything obvious. There was a little bit of corrosion on the contacts so I replaced the cap with a new one, fired it up and it ran till it warmed up. I shut the engine off and it would not start back up again. Threw a P1320 code so I dug up my old distributor to replace the "new" one. I noticed the shaft on the "new" distributor doesn't rotate smoothly. There's a little resistance while rotating than it get's easier than it kinda falls into place. I replaced the distributor, timed and took her for a quick drive. Seems to be running better but I won't know till a drive more.

I took off one of the hoses from the air intake to gain more access to the harnesses and found a little surprise.


I was told this was PCV and could very well be causing all of my headaches.

[AU Qx4]

Hey Merrix, I am new as well but have been working on Nissans a long time.

Your above picture is why you shouldn't drink while repairing cars. Wait until your done!

I had some very similar symptoms from a badly oil fouled IACV (intake air control valve), these need to be removed and cleaned regularly. This could also be related to fouling of o2 sensors.

On my year, if the gasket fails, it will short out the ECM so I check it every 30k.

[AU Qx4]

Also, make sure your coil wire has good corrosion free contacts on both ends. My 95 had that issue also.

[Merrix]

Hey Merrix, I am new as well but have been working on Nissans a long time.

Your above picture is why you shouldn't drink while repairing cars. Wait until your done!

I had some very similar symptoms from a badly oil fouled IACV (intake air control valve), these need to be removed and cleaned regularly. This could also be related to fouling of o2 sensors.

On my year, if the gasket fails, it will short out the ECM so I check it every 30k.

Drinking while working on cars is one of the only ways to get through all the anguish of diagnosing! Fortunately, I had never removed that PCV hose nor used a pipe cleaner haha. So I know it wasn't me.

I'll look into that IACV tonight! That's good information. Thank you!

[Merrix]

Took her for a good test drive last night and still same symptoms as before. Looks like next step is the IACV and of course it's buried under the plenum. Might as well replace other goodies underneath there while it's off.

How common is it for the IACV to fail? Is there a way or trick to clean the valve without removing the plenum?

[MisterH]

If you saying "...same symptoms as before" does that mean you're you still getting DTC P1320?

[Merrix]

If you saying "...same symptoms as before" does that mean you're you still getting DTC P1320?

Oops. Forgot to mention that. I not haven't gotten the P1320 code since replacing the distrubor. But as far as rough idle and stalling, that's still an issue. Also hesitation at freeway cruising speeds. Engine speed between 2k and 3k rpm. I'm replacing both upstream O2 sensors today.

[Wrierblock20]

Sounds exactly like my issue I just fixed except I did not get stall you should run some Royal Purple MAX injector cleaner in 10gal of gas I ran a full bottle in around 7gal see if any improvement if so sounds like clogged injector I was getting multi misfire then I ran the cleaner and chaned dizzy + fuel filter after that I got cyl 2 misfire, ended up changing the #2 fuel injector.

[Merrix]

I've ran a few cans of seafoam through my tank and it really didn't make a difference. I'll try the Royal purple though and see what happens. Wouldn't bad injectors or miss fires throw a code? I haven't gotten and codes for either of them.

After replacing my upstream O2 sensors the engine definitely runs better but I'm still having the same symptoms but nowhere near as bad. I think my next part will be the MAF sensor.

[macgiver]

mac,I had very same 1500 rpm - 3200 rpm slaggish acceleration with codes indicating -coolant temp sensor / ckt. , Left O2 sensor / ckt. , and Knock sensor /ckt . I am a mechanic/electrician , I componant checked & connector checked all - Knock sensor (inside - under intake plenum ) checked as open ckt , should've been several hundred Ohms I believe! It had probably been intermittant from similar mysterious occurances in recent past - BUT it CAUSED ALL OTHER CODES !!! Completely corrected the lag from off-idle to mid-range power I was able to relocate to an external,"top of the manifold" spot that worked just as well. Be sure to eliminate PCV valve('s) for they may mimic this situation. Lastly better check , re-adjust / "play" with base timing -if adjustable , is where you can really pull all the horses out of the stall !!

[Merrix]

mac,I had very same 1500 rpm - 3200 rpm slaggish acceleration with codes indicating -coolant temp sensor / ckt. , Left O2 sensor / ckt. , and Knock sensor /ckt . I am a mechanic/electrician , I componant checked & connector checked all - Knock sensor (inside - under intake plenum ) checked as open ckt , should've been several hundred Ohms I believe! It had probably been intermittant from similar mysterious occurances in recent past - BUT it CAUSED ALL OTHER CODES !!! Completely corrected the lag from off-idle to mid-range power I was able to relocate to an external,"top of the manifold" spot that worked just as well. Be sure to eliminate PCV valve('s) for they may mimic this situation. Lastly better check , re-adjust / "play" with base timing -if adjustable , is where you can really pull all the horses out of the stall !!

My knock sensor has yet to turn my check engine light in but every time I pull codes I get the knock sensor code. I might as well replace that while the plenum is off. You're saying that my symptoms could be caused by a faulty knock sensor?

[macgiver]

mac , Another forgotten aspect , I forgot to mention is - Check Engine Light (MIL) DOES NOT COME ON FOR ALL the CODES ALL of the TIME - maybe for your case but my situation I mentioned ,knock ONLY codes - NO LIGHT , 5 total codes in my J30 don't Light the MIL , amongst them : code 11=crank sensor ,code 21=Ign. signal ckt. ,code 42=fuel temp sensor , and code 54 =A/T to ECM . Look in your FSM this must be to a degree similar across Nissan / INFINITI , for after '93 man there's over a hundred codes NOT ALL DEEMED IMPORTANT enough to "Alarm" owners & Light that MIL - people would be pissed for one Check the FSM for your vehicle and ya gotta simply "scan" periodically for a truer picture
p.s. Answer YES to knock sensor "possibility", it's supposed to be a "Piezo-Electric Microphone", a very high impedance , measure 500k - 700k Ohm , mine read"Open ckt." on meter , or Infinity Ohms ,& bolting a NEW one in is ALL SHE TOOK ! Again if that seems to do it - MAXIMIZE the FIX by chk. , adj. , set , "play" with base timing (if adjustable). If it's inside the plenum YOUR TAKING OFF ?? Yes it would be FOOOOLISH to not put a NEW ($125 part ) in there .

[Merrix]

Update: I replaced my distributor with a warranty distributor last Saturday as well as diagnosed the wire harnesses and ECM for MAF and knock and everything checked out. After about 100 miles of driving, still the same symptoms. Maybe even a little worse. I think my timing is off a little. I have yet to remove the plenum and replace the knock sensor and clean IACV which unfortunately I wont be able to do that till next weekend but that is the next big task. A friend has the Infiniti version of my pathfinder so some time this week I am going to install his MAF in my car and see if that changes anything. Hoping it will so I can finally pinpoint this nightmare of mine. Not looking forward to the price tag that comes with a new MAF though. Definitely need to shop around for that.

[Merrix]

Late update: Turned out the stalling and rough idle was caused by a bad MAF. Luckily I have a friend that works for Napa. $200 turned into $68.