RPM too slow to idle range

Hi Friends,

I see a problem in my Logan 1.6 GLS related to RPM. I am listing some scenarios and the observations in my car. Let me know if this is normal and you all face the same observation.

Scenario 1. The car is in 5th gear, I accelerate the car and the car is moving at 100 Kmph, the RPM is around 2000. I release the accelerator completely, press the clutch and move the gear to neutral. The car moves on the momentum for quite some distance.

Observation: Usually, the RPM would come down gradually to idle range (750) after 3 to 4 seconds of moving the gear to neutral. But sometimes, the RPM stays at 1500 as long as the car is moving. If the car moves for say 5 minutes on the momentum, the RPM stays at 1500 for 5 minutes. If I apply brakes and stop the car, only then the RPM comes down to idle RPM, that too after 5 seconds of stopping the car.

Scenario 2. The car is in 2nd/3rd gear, I accelerate the car and due to some traffic, I had to stop the car. I release the accelerator, apply clutch and move the gear to neutral and apply brakes.

Observation: Usually, the RPM would come down gradually to idle range (750) after 3 to 4 seconds of moving the gear to neutral. But sometimes, the RPM stays at 1500 range and falls to the idle range after around 10 seconds and sometimes it stays there permenantly. To bring the RPM down, I have to change to 1st or 2nd gear, release the clutch a bit.

Please note that I don't use any floor mats and when the RPM stays, I could hear the engine raising noise (the noise will be similar to what if you press accelerator and try to maintain the RPM at 1500 range, when the gear is in neutral).

Thanks,
Krishna

i didn't find the RPM drop sharply (like our Ambassadors used to) on taking your foot off the accelerator in any of the newer age cars provided you are on a flat, non bumpy road... i dont know the technology well enough to comment, but i think that's the way gear boxes are designed... and i use this to my advantage in driving.. it is much easier to hold speed ...

the way i look at it is.. accelerators are there for accelerating.. brakes are there to decelerate..
why do i need the engine to slow down th ecar for me? let the engine run as per my last instruction..

Did you have your a/c on or off during the times you noticed this? The engine adds to the deacceleration. In Diesel engines the rate of deacceleration is easily noticeable when one is shifting gears and holding brake to bring the speed down.
The technolgy in the Ambassador is outdated. The newer models of Ambassador have some of the latest technology incorporated into them. In the newer cars its the ECU that does all the calculations.

@krishnakumar
your scenario 1 seems to be normal.

however scenario 2 does not seem to be normal where the needle stays where it is and then you have to change to 1st or 2nd gear release the clutch a bit to bring the RPM down.

something wrong with your RPM meter probably. get it checked.

A side observation - if your car is in motion , you souldn't be shouldn't be shifting to neutral in the first place..ideally you should apply brakes gently while downshifting through the gears..

Ok just for a check YOU can all do this if you have a computer in your logan
press the button in front of the tacho and keep it pressed now turn ON the ign the cars electrics will now go through a test phrase
Stu

Thanks a lot for the replies.

I think I confused it a bit by those long sentences.

What I want to know is, if you are traveling at a speed of more than 70KMPH, release the accelerator, press the clutch, move the gear to neutral. What happens to the RPM in your car?

For me, most times, the RPM reduces gradually (within around 3 to 4 secs) to Idle range. This is the normal behaviour. But, at times, it stays there at 1500 as long as the vehicle runs and the engine noise could be heard inside. This is the problem.

Hi,

Ya, I agree that RPM will not drop immediately after taking the foot off the accelerator. But, it will definetely drop after you press the clutch and move to neutral.

Logan_loverinDelhi wrote:

i didn't find the RPM drop sharply (like our Ambassadors used to) on taking your foot off the accelerator in any of the newer age cars provided you are on a flat, non bumpy road... i dont know the technology well enough to comment, but i think that's the way gear boxes are designed... and i use this to my advantage in driving.. it is much easier to hold speed ...

the way i look at it is.. accelerators are there for accelerating.. brakes are there to decelerate..
why do i need the engine to slow down th ecar for me? let the engine run as per my last instruction..

Hi Mir,

For you, does the RPM stay at high range even if you move to neutral when the car is moving?

Mir... wrote:

@krishnakumar
your scenario 1 seems to be normal.

however scenario 2 does not seem to be normal where the needle stays where it is and then you have to change to 1st or 2nd gear release the clutch a bit to bring the RPM down.

something wrong with your RPM meter probably. get it checked.

KrishnaKumar wrote:

Thanks a lot for the replies.

For me, most times, the RPM reduces gradually (within around 3 to 4 secs) to Idle range. This is the normal behaviour. But, at times, it stays there at 1500 as long as the vehicle runs and the engine noise could be heard inside. This is the problem.

if this is the problem then i would ask you to check the position of the floor mat.. it often gets stuck with the clutch and/or the accelerator

A: You are not being clear as to whether the AC was running. If so this could be a cause, depending on the weather during your test drive.

B: Just a suggestion, when releasing accelerator and after getting in to neutral, slip your foot below accelerator pedal and pull it upwards, to see fo there is some more movement that is being obstructed by a stuck accelerator.

@ Tomlai, that is a valid point.

Ideally, once pulled in neutral, the rpm is supposed to fall down.

KrishnaKumar wrote:

Hi Mir,
For you, does the RPM stay at high range even if you move to neutral when the car is moving?

NO. It gradually drops.

KrishnaKumar wrote:

What I want to know is, if you are traveling at a speed of more than 70KMPH, release the accelerator, press the clutch, move the gear to neutral. What happens to the RPM in your car?

It gradually drops.

What KrishnaKumar is not verifying is whether his AC was on or not during this problem. Eevrything else can only be discussed meaningfully thereafter.....

@tomlai: Good Point...
@krishnakumar: What is the rpm when your car is stationary but with engine on?
Say it is X. So whenever you slow down with neutral your rpm must get back to that X gradually irrespective of A.C. on or off.

On mine it is set to some 1000 and the needle does not go below this with engine on.

Mine is set to 850 But I have no AC (Dont need em here )

Krishna,
Have u visited the service center with this problem??
If u are saying,at times the RPM doesnt drop for about 5 mins(tats HUGE) after neutral, there is a problem with the car computer! Go to the service center and they'll probably reset it.
DO NOT DELAY THIS!

Unplug the battery for 5 mins ! this will reset the computer for you

Hi All,

Thanks a lot for your replies.

I had seen the problem with both AC on and Off.

I tried to get it fixed for the past 2-3 months taking the car to service center for more than 7 times and every time the service center returned back saying they were not able to see the issue during their test drive.

I finally contacted Mahindra Customer care and they understood the seriousness of the issue and some engineers from Mumbai have visited the service center to solve the problem this week. I also showed them a 3 minute video clip in which the car was at rest, gear was at neutral, accelerator, clutch and brakes were free and the RPM was at 1500 for more than 3 minutes. They are now analyzing the issue.

very new kinda problem heard by me...


kindly update soon what was done to resolve it

waiting?????

Probably some ECU corruption or some sensor problem?

Since the problem happens very inconsistently, even the technical people from Mahindra were not able to see the problem during their test drive. I was later told that they saw the video clip and they have changed all the components that COULD possibly lead to the problem:shock:. I wonder if the root cause of the problem has been fixed.

Here is the list of spare parth they changed:
- TUBE-GAS VAPOR ABS
- SEAL 1-AIR INTAKE MANIFOLD
- MANIFOLD 1-AIR INTAKE
- UNIT-THROTTLE MECHANICAL

Any idea on what these are and why they have touched these parts?

Usually, after the lubrications/adjustments done during the service, for a couple of days, the problem would not happen at all. So, I will drive the car frequently for the next couple of weeks and see if it is resolved.

It seems that your erratic idling was because of a throttle position sensor malfunction (the parts changed seem to indicate that).

For an explanation of what this part does, see - http://en.wikipedia.org/wiki/Throttle_position_sensor

i am learning a lot things here


thank you all of you guys

Hmm. Pretty interesting case study. Some really rare cases being addressed here i guess.