Rough Idle with A/C

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A1218
Posts: 308
Joined: Thu Aug 06, 2020 6:03 pm
Car: 1997 Nissan Pathfinder SE

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On my 97 Pathfinder I've noticed that the vehicle idles a bit rougher with the A/C system on. Not by a drastic amount but just enough that you notice it when the a/c is on.

Also with the a/c on and you accelerate sometimes you would hear a slight rattle noise. Sometimes its there and sometimes its not. But never with the a/c off. Ive tried to listen for the noise from the engine bay with the hood open but cannot hear anything. Only when inside and cabin is quiet you hear it. But it does not sound like its coming from inside vehicle.

The a/c compressor is new along with the dryer/accumulator. It has been vacuumed and recharged. Did this repair about a week ago.

I've had this noise even before I had the work done on a/c system.

Everything is maintained well on the vehicle such as plugs, oil, filters, fuel filter, new maf sensor, new tps sensor, cleaned throttle body, etc. In the past month I have also changed a few of those small vacuum lines. Is this normal operation when the a/c is on?

The only code I have is a P1441 code that comes and goes and that has been there for 2 years now. Cannot narrow down that issue as I have changed the vacuum cut bypass valve and solenoid and code still comes back. The evap canister was replaced once.


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mdmellott
Posts: 1147
Joined: Mon Sep 02, 2019 3:32 pm
Car: '13 Kia Soul+ 2.0L AT
'02 Pathfinder SE 3.5L AT P/4WD
Location: SF Bay Area, CA

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That P1441 trouble code indicates a very small leak somewhere related to the EVAP system. https://www.engine-codes.com/p1441_nissan.html#causes This small vacuum leak may be the cause of your idle being rough when your A/C is on. Your ECM will adjust the idle as it tries to compensate for the additional load on the engine when the A/C is on. The small vacuum leak will cause problems with the idle. An old fuel fill cap that no longer seals well is a common cause of this type of leak since it wears out over time with continuous use filling your gas tank. Check all your EVAP system vacuum hoses for cracks and be sure they all fit air tight where they are installed. As for the intermittent slight rattle noise, that's too vague of a description for me to even guess what it might be. Fix the P1441 code problem and perhaps everything will go back to normal.

A1218
Posts: 308
Joined: Thu Aug 06, 2020 6:03 pm
Car: 1997 Nissan Pathfinder SE

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Yeah I ordered a filler cap a few days ago as I realized that the tank doesn’t have pressure when removing cap and also get a smell of gas at the back.

However I’ve also recently noticed that the vehicle hard starts sometimes and the rpm slowly rises. The first cold start in morning is fine but sometimes after it hard starts. Not necessarily a heat soak like issue. Even if I were to do a cold start in morning and after a minute I shut off and restart, you get the hard start.

I’m not sure if this could be related to evap also.

Thank you

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mdmellott
Posts: 1147
Joined: Mon Sep 02, 2019 3:32 pm
Car: '13 Kia Soul+ 2.0L AT
'02 Pathfinder SE 3.5L AT P/4WD
Location: SF Bay Area, CA

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Check the voltage output at the battery terminals with and without the engine running before you drive the car that day. Use a decent voltmeter. A perfectly good battery should measure 12.6V without the engine running. If it measures below 12V either your battery might be getting old and can't hold a charge or your alternator might not be doing its job to keep it fully charged. With the engine running and all accessories turned off, the measured voltage should be about 14V which would indicate your alternator is working well. If the voltage is down around 13V, your alternator may be getting weak. Measure the voltage again with your A/C on and the fan on high. If the voltage drops way below 13V, your alternator may be getting worn out. When the alternator is hot, it is a bit less efficient than when it is cold, which might explain why your car has a harder time starting after it has already been warmed up.

A1218
Posts: 308
Joined: Thu Aug 06, 2020 6:03 pm
Car: 1997 Nissan Pathfinder SE

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I put in a new battery about 6 months ago (Autozone duralast gold), but would still check it because you never know. And the alternator is tested straight from the battery terminals also?

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mdmellott
Posts: 1147
Joined: Mon Sep 02, 2019 3:32 pm
Car: '13 Kia Soul+ 2.0L AT
'02 Pathfinder SE 3.5L AT P/4WD
Location: SF Bay Area, CA

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Yep. Here are a couple of video clips of doing just that.
https://www.youtube.com/watch?v=Bzz7P3qNHcE
https://www.youtube.com/watch?v=LGB6ZEjGm7Q

A1218
Posts: 308
Joined: Thu Aug 06, 2020 6:03 pm
Car: 1997 Nissan Pathfinder SE

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Thanks I’ll try this out and share the info tomorrow.

I had one more question, do you think the evap purge control valve under the hood can cause this? It ticks sometimes but I don’t know if that’s normal operation. It has the electrical connection and was wondering if I can unplug it to also see if I get an improvement in that slight rough idle. That way I know if I need to change it.

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mdmellott
Posts: 1147
Joined: Mon Sep 02, 2019 3:32 pm
Car: '13 Kia Soul+ 2.0L AT
'02 Pathfinder SE 3.5L AT P/4WD
Location: SF Bay Area, CA

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If the EVAP purge control valve has a slow leak it could cause an idle issue but unplugging it won't help. It will still leak, if it is leaking, and you would likely get another DTC flagged because the unplugged purge control valve would not function at all during the self diagnostic start up check when you start up the engine. The following link to the factory service manual for your '97 Pathfinder will show you all the EVAP system parts and hoses on pages EC-20 to EC-23. https://www.nicoclub.com/service-manual ... 997/ec.pdf It might help you track down the leak if it isn't just the gas cap you have already ordered as a replacement. The tick noise you hear from the purge control valve, after you start the engine, is the valve being actuated during the self diagnostic check which is performed by the ECM every time you start the engine.


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