Low engine idle?

NAJEEBYAHIYA

MEMBER
2016 TOYOTA RAV4
2.5L
4 CYL
2WD
AUTOMATIC
100,000 MILES

Car RPMs go down to 500 RPMs and vibrates when it's idling in drive or reverse. (When I press brake and car not moving) But when I shift to neutral its normal around 800 to 900. No issues while driving. No misfire. No bad gas mileage.

Note that RPMs becomes normal when I turn on A/C or headlights.

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,772 POSTS

Hi,

When you turn the A/C on, the computer compensates for the added load by increasing the idle speed. So, we know the idle air control circuit is working.

My next suspect is you may have an engine vacuum leak. I would start by checking if anything is damaged, disconnected, or loose.

Here is a link that explains how to check:

If I had to guess, this is what I suspect is the issue.

Here is another link that describes common symptoms related to the:

https://www.2carpros.com/articles/7-common-symptoms-of-a-vacuum-leak-in-your-car-how-to

Let me know what you find.

Take care,

Joe

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Thursday, March 16th, 2023 AT 8:53 PM

NAJEEBYAHIYA

MEMBER
2 POSTS

Thank you for your reply. I have inspected myself for vacuum leaks. I will check again with a mechanic soon.

Yesterday I disconnected the Stop light fuse. And shifted gear to drive. (So, brake lights won't turn on when I hold the brake). RPMs didn't go low. Do you think there will be other reason other than vacuum leaks?

I checked battery voltage with alternator on and off, it's all good.

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Friday, March 17th, 2023 AT 3:55 AM

JACOBANDNICKOLAS

MECHANIC
109,772 POSTS

Hi,

Yes, there could be an issue with the idle speed control circuit. The standard idle speed:
is between 720 to 820 rpms in neutral or park. Once in gear, that will lessen. This is why I'm questioning a vacuum leak. You really aren't far out of what I would consider normal and the rough idle is often indicative of a vacuum leak.

Let me know.

Joe

Let me know if I can help or if you have other questions.

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Friday, March 17th, 2023 AT 8:03 PM