Uneven idle speed when idling in drive with the air-conditioning on and transmission in drive at the stoplight?

Tiny
ALEX STATHAS
  • MEMBER
  • 2014 NISSAN VERSA
  • 1.6L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 85,500 MILES
Hi, when I stop at the red lights and I have the air-conditioning on I notice that the tachometer rpm fluctuates between 500 RPMs and 1,000 RPMs, but the check engine light won't come on to give me any codes, it just idles unevenly with the air-conditioning on. Could it be the air-conditioning cycling pressure switch? The PCV valve? The charcoal canister or charcoal canister purge solenoid? I don't know which other sensors or solenoids to name as the possible culprits because I don't know much about cars, thank you in advance for your help. Alex Stathas
Thursday, February 9th, 2023 AT 12:00 AM

5 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi,

The first thing I'm going to recommend is to check the wiring and connector at the throttle control actuator. See pic 1 below.

The ECM controls the engine idle speed to a specified level through the fine adjustment of the air, which is let into the intake manifold by operating the electric throttle control actuator. When you run the A/C, there is an added load on the engine and the ECM needs to control the actuator to increase the idle speed to compensate for the added load.

In this case, the actuator may be failing, or you could simply have an engine vacuum leak. So, if the wiring appears to be in good condition, free of corrosion or dirt, and the connector is tight and not damaged, I would recommend checking for leaks. Here is a link that explains how it's done:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know what you find.

Take care,

Joe

See pic below.
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Thursday, February 9th, 2023 AT 1:48 PM
Tiny
ALEX STATHAS
  • MEMBER
  • 71 POSTS
Yes, I noticed the electronic throttle control actuator even before the rough idle with the air-conditioning on, the electronic throttle control actuator takes the place of the throttle cable in older cars, I am too scared to mess with the engine electronics because I am afraid of causing a no start condition and I can't take it to the repair shop because I am afraid they will charge me a small fortune. Also, I can't mess with the vacuum hoses because I am afraid of causing stalling. So, I will have to live with the rough idle and hope that the three-month interval bulk synthetic oil changes at Walmart will keep the engine from seizing up. Your reply was very informative though. Thank you very much.
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Thursday, February 9th, 2023 AT 2:20 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi,

I understand your concerns. However, take a minute and just inspect the vacuum hoses. You may find one disconnected or cracked. Honestly, unless you disconnect many of them, you won't cause a no-start condition. The same with the actuator. Simply inspect the connector to make sure nothing appears damaged. If you want, you can take a few pictures and upload them for me to see. I will try my best to identify any possible issues and let you know.

Regardless, it is up to you. I understand your concerns. I'm here if you need anything. Let me know if I can help you in any way.

Take care,

Joe
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Thursday, February 9th, 2023 AT 5:57 PM
Tiny
ALEX STATHAS
  • MEMBER
  • 71 POSTS
Hi, I am computer illiterate and so I don't know how to upload or download pictures, all I can do in the computer is type text and click the blue reply button, earlier I also forgot to mention that when the uneven idle rpm goes down to 500 rpm the engine shakes and acts like it's going to stall and when the idle rpm goes back up the engine smooths out, so far with the frequent bulk synthetic oil changes at Walmart I have avoided the engine seizing up or the crankshaft and bearings jamming to each other and fusing or melting together, but you are right I can inspect the hoses for cracks and I can inspect the electrical connector of the electronic throttle control actuator without causing any stalling or no-start condition as long as I visually inspect the hoses and actuator without touching them or messing with them, but I can't go to the repair shop because auto repairs have become prohibitively expensive and I can't switch to a new car because they don't have the Nissan Versa anymore they only have the Nissan Sentra which retails for over $22,000 dollars for a used 2022 model not a new 2023 model, but thank you for informing me on how I can visually inspect the vacuum hoses and electronic throttle control actuator without touching them or messing with them and making the problem worse. Alex Stathas
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Friday, February 10th, 2023 AT 12:01 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Alex,

The prices of everything are out of control. I would have retired in two years, but my pension is based on the last 30 years. I won't survive. I don't have a second chance to go back and make more. I completely understand your frustrations.

Listen, I'm here if you need help. Let me know if you have questions anytime. We are all in this together. LOL

Take care,

Joe
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Friday, February 10th, 2023 AT 8:40 PM

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