Rpm's Increase When Car Is In Park Or Neutral. Why?

nuwannisha · August 24, 2015

When my car is set in drive and I have my foot on the brake, it averages around 1,000 RPM. For some reason though, when I put my car into park or neutral the RPM's average about 2500. Why is that?

tiv · August 24, 2015

You should specify the car make/ model/ YOM mate

matroska · August 24, 2015

I had a similar experience once and it turned out to be a damaged vacuum tube. (there was a leak in the vacuum tube). but depending on the vehicle it could change so please provide the model of your car and the good folk here will help you.

gNaveendra · August 24, 2015

Try to refer the discussions below.

Sometimes you could get some idea.

http://forum.autolanka.com/topic/16976-rpm-meter/

http://forum.autolanka.com/topic/16465-idle-state-rpm/#entry268683

http://forum.autolanka.com/topic/11506-rpm-idle/

asrock · August 24, 2015

malfunctoning ICV?

Rumesh88 · August 24, 2015

@nuwannisha - Welcome to the forum!

Does your car start normally on cold start ie with the engine cold and gear in P if you start does it rev up to around 1500 to 2000 RPM first and then drop down to around 1000 as the engine warms up? Also what's your car model?

Pericles · August 25, 2015

2500? That sounds quite excessive no matter what the car. You sure about your numbers?

nuwannisha · August 25, 2015

Its NISSAN Bluebird sylphy 2001 model

nuwannisha · August 25, 2015

In N or P position,Rpm spins between 2000-2500.sometimes it happens in hot condition also. one of my friend tried to run LEARN program using OBD scanner. but it was unsuccessful.

Rumesh88 · August 26, 2015

On 8/25/2015 at 4:04 PM, nuwannisha said:
In N or P position,Rpm spins between 2000-2500.sometimes it happens in hot condition also. one of my friend tried to run LEARN program using OBD scanner. but it was unsuccessful.

That's not what I asked for. Let's go through it again. When you start the car for the first time in the morning (ie engine cold, gear in P, AC and headlights off),

1. what's the initial RPM? and

2. if you leave the car to idle for 3 minutes (gear still in P) of idling does the temperature come close to half-mark on the indicator? and

3. if so, what is the RPM after 3 minutes? (if you live in a cold climate may have to extend the time a bit)

4. How long does it take for the temperature to come close to the half-mark?

This observation would clear a few things like whether the IACV and associated sensors are working normally etc.. Also you say the idle RPM in D is around 1000 is this with AC on or off? (cos that also seems to be bit too high)

NRX · August 26, 2015

Did someone mess with the throttle body area ? You might need to hook up your car to a scanner and perform an "Idle air re-learn"

nuwannisha · August 26, 2015

On 8/26/2015 at 2:57 AM, Rumesh88 said:
That's not what I asked for. Let's go through it again. When you start the car for the first time in the morning (ie engine cold, gear in P, AC and headlights off),
1. what's the initial RPM? and

2. if you leave the car to idle for 3 minutes (gear still in P) of idling does the temperature come close to half-mark on the indicator? and

3. if so, what is the RPM after 3 minutes? (if you live in a cold climate may have to extend the time a bit)

4. How long does it take for the temperature to come close to the half-mark?

This observation would clear a few things like whether the IACV and associated sensors are working normally etc.. Also you say the idle RPM in D is around 1000 is this with AC on or off? (cos that also seems to be bit too high)

1.around 1500 rpm

2.no

3.around 1000

4.7-10 min

there was a trouble last night. when i was in traffic, engine stopped suddenly (i was in D position). i tried to restart the engine but i was unable to start.then i switched off all accessories and wait about 2 min. then i was able to start .then idle rpm was around 2500. when i put it in to D position it was around 1500.when i put it again in N or P position it was around 2500.

nuwannisha · August 26, 2015

On 8/26/2015 at 3:36 AM, NRX said:
Did someone mess with the throttle body area ? You might need to hook up your car to a scanner and perform an "Idle air re-learn"

I tried to do it but Idle Air re-Learn was unsuccessful.

Rumesh88 · August 26, 2015

On 8/26/2015 at 6:13 AM, nuwannisha said:
1.around 1500 rpm
2.no

3.around 1000

4.7-10 min

there was a trouble last night. when i was in traffic, engine stopped suddenly (i was in D position). i tried to restart the engine but i was unable to start.then i switched off all accessories and wait about 2 min. then i was able to start .then idle rpm was around 2500. when i put it in to D position it was around 1500.when i put it again in N or P position it was around 2500.

From your observation I noticed a few things.

1. Your IACV is working but may be getting stuck at times if the fault (getting to 2500 RPM) is intermittent.

2. As NRX says someone may have messed up with the throttle close position adjustment or a vacuum line.

3. Someone may have removed the thermostat valve but it is not related to this issue. Ignore it for the moment.

4. Another possibility (most likely one IMO) is that your Throttle Position Sensor is faulty and giving an erroneous signal to the ECU.