idle drops when coming to stop

[Derek]

I'm trying to determine whether this is anything to be concerned about. I just purchased an '07 SR5 V6 2WD with ~65K miles on it. One thing I've noticed, especially during stop-and-go rush hour traffic, is that often when coming to a stop the idle drops down to around 500 RPM and then bounces back up to around 600-700 RPM. Even if I'm only going 5 MPH, then press the brakes to stop, the idle drops down to the 500 RPM mark and you can feel the idle drop as well.

Is this normal? Anything to worry about?

 

[20034RunnerV84x2]

Bad tank of gas, bad spark plugs can also cause this. It has 65k so the spark plugs should have been changed 2 times by now.

 

[Derek]

Bad tank of gas, bad spark plugs can also cause this. It has 65k so the spark plugs should have been changed 2 times by now.

Thanks for the reply. I didn't think of the spark plugs. I have the service records provided by Toyota and the previous owner did all of the recommended maintenance, but I'm not sure the plugs were ever changed. This is my first venture into the world of buying used vehicles. The last 4Runner I purchased was new back in '05. I should have kept that one... Live and learn.

 

[aeroneer1]

Or could need to clean your mass air flow sensor and throttle body. Or could have a vacuum leak. When you hit the breaks the vacuum system reacts for example.

 

[galactic_04]

Clean your throttle body. My brother saw this all the time at the dealer. Too much build-up around the "butterfly valve" in the intake causes the idle to drop too far. A little carb cleaner and a rag will fix the issue.

 

[Derek]

Clean your throttle body. My brother saw this all the time at the dealer. Too much build-up around the "butterfly valve" in the intake causes the idle to drop too far. A little carb cleaner and a rag will fix the issue.

THANK YOU! I tried what you suggested today and it appears to be idling much better. This is why I love this forum. :bigok:

:cheers:

 

[FooJet]

Just bought a 08 4Runner. Mine idles between 500-600 rpms at stop. Is this the correct idle?

 

[Jeff4runner]

Or could need to clean your mass air flow sensor and throttle body. Or could have a vacuum leak. When you hit the breaks the vacuum system reacts for example.

Power brakes are all electronic on the 4th generation. They have a combination ABS, power brake electric pump, so no vacuum lines or pancake booster. Most likely plugs, or butterfly valve. In addition, the 4th gen does have a feature where it slows the engine RPM down electronically when the brakes are depressed, for safety reasons. A good test for this would be to have the engine warmed up fully, idle in drive, and let off the brakes and see if the rpm moves slightly. 500-550 idle rpm in stop and go is not harmful, but when you start getting into the 400s, then you have an issue.

 

[Jeff4runner]

Just bought a 08 4Runner. Mine idles between 500-600 rpms at stop. Is this the correct idle?

500-600 is perfect, and 600-650 with the A/C compressor engaged.

 

[Krazynative]

Mine has done this since day one and I bought it new. I think I remember reading in the manual that it helps with starting on a hill so you don't roll backwards. Or I could have dust dreamed it. Either way I like this feature. It makes it easier in stop and go traffic and of course on mellow inclines.

 

[FooJet]

500-600 is perfect, and 600-650 with the A/C compressor engaged.

Great. Thanks Jeff4Runner!

 

[Derek]

Mine still seems to be dropping to the 500 RPM range while idling and stopped. It seems to fluctuate between 500 and 600 all the time, regardless of whether the A/C is on. What concerns me is that you can feel the idle when it drops to 500, as in you can feel the vibration. I will be changing the spark plugs this weekend since I suspect that the originals have 68K miles on them. I'm hoping this helps.

 

[Krazynative]

Mine still seems to be dropping to the 500 RPM range while idling and stopped. It seems to fluctuate between 500 and 600 all the time, regardless of whether the A/C is on. What concerns me is that you can feel the idle when it drops to 500, as in you can feel the vibration. I will be changing the spark plugs this weekend since I suspect that the originals have 68K miles on them. I'm hoping this helps.

Definitely change the spark plugs. For some reason the dealers all think that the stock plugs are good for 100K, but they are not. The plugs that come with the T4R are 30K plugs. You can get the 100K ones tho. Do a search and you will find tons of threads on this.

The stock plugs are different on each head. NGK on one and Nippondenso on the other (or something like this). that is the way to tell if they have ever been changed. I noticed a much smoother running motor after my plug swap. I did mine at about 45K.

 

[Derek]

I just wanted to provide an update. Since creating this thread I have:

- Cleaned the throttle body

- Replaced the air filter

- Replaced the spark plugs (this was overdue as the original ones were still installed with 68K miles on them)

- Cleaned the Mass Air Flow Sensor

After doing all of this, the problem was still there, although not as bad. So, finally after doing some more reading I learned that the computer may just need a simple reset by disconnecting the battery. So I disconnected the battery a few days ago and left it disconnected for an hour. After reconnecting it, and then driving around for a few days I am happy to report that the idle appears to be normal for the first time. Thanks again for all the help!

:bigok: