[TheMileCruncher]

Originally Posted by Chethan B G

Few reasons for Idle RPM increase are; battery is weak or the alternator is not charging properly or the AC compressor/temperature sensor is not working or a bad ground/return path or leak in air intake.

If an electrical accessory has to create an issue, then there can be two reasons; either the accessory is defective / of low quality in terms of wiring which has eventually failed or the battery is weak.

It is a good idea to start adding one accessory per day. But before that, I would blindly replace the battery if it is more than 3 years old.

All the best! Please update!

I got the battery load tested over the weekend from a local store and the battery is absolutely fine. Then I checked the alternator by disconnecting the negative battery terminal while the engine was running and did not notice any changes in the idle RPM.

I have reconnected the security system and amplifiers back and do not see the high RPM issue anymore. The only other item that needs to be reconnected is the fog lamp and the secondary horn which I'll do sometime later this week and update the thread with the results.

Originally Posted by SCORPION

It is possible that the engineer quietly replaced your oxygen sensor to save the dealer workshop from embarrassment. Faulty oxygen sensor in the exhaust manifold can cause rough, erratic idling and can also cause the car to stall. I had a similar issue in one of my earlier cars and the oxygen sensor was the culprit. The car did not display the Check Engine Light.

Even I suspect the same, however, there is no way for me to find that out. I'm now using an OBD scanner and the O2 sensor readings are within normal range. BTW, the CAT CON on my car was also replaced a few months ago since it had gone bad. One of the causes for the CAT CON to go bad is also a bad O2 sensor but this wasn't changed the last time since the MASS guys did not find any error for this in the ECU. Maybe it was the O2 sensor.

Originally Posted by scorpian

Hi,
You will need to isolate all accessories one by one and that should help you pinpoint where exactly the issue is.
If you can then start isolating each circuit by removing the respective fuse from its holder and then observe if the issue is resolved or still occurring, if its still present then some other accessory is causing a issue and then you move to that particular fuse.
Your best bet is to eliminate each circuit one by one,eventually you will be able to find out whats causing the issue.

I'm doing this the other way around. I am adding each accessory back one by one and so far, no issues. Once I have all the circuits connected, I plan on going back to the MASS engineer and ask him to explain.

Originally Posted by SS-Traveller

Very typical of a sparking electrical connection somewhere - a loose earthing point, or a badly jointed wire, or a short circuit.

So far, did not find any issue but I'm going to get this thoroughly checked soon.

Originally Posted by Aroy

High idling may be the ECU trying to get sufficient RPM to charge the battery. That can be due to any one of the following :
. Battery on its last leg. The normal RPM is not enough to charge.
. Alternator has deteriorated, so that it cannot charge at normal idling RPM.
. One or more accessory is consuming more power than the alternator can supply at idling.

You can home in a step by step manner.
. Get the alternator and battery checked by a third party electrical shop, who have the necessary test equipment. This is quite routine - current output for alternator, and discharge test for battery.
. In case both are fine, then start by connecting one accessory at a time and check the current consumed.
. In case all seems fine, then as others have pointed out it may be an earth loose or a short in harness.

You should find the culprit if it is any of the above.

The harness was checked by MASS and they claim that there is no problem with it.

Unfortunately, a rat entered the engine bay yesterday afternoon and chewed off a lot of wires that were connected to the accessories. I've had to disconnect everything (except for the amps) and now I plan to get the wiring redone sometime this week.

Once everything is in place, I'll be able to confirm if the issue is due to the extra accessories or something is wrong in the car itself.

Thanks for the help!

[SCORPION]

Originally Posted by TheMileCruncher

BTW, the CAT CON on my car was also replaced a few months ago since it had gone bad. One of the causes for the CAT CON to go bad is also a bad O2 sensor but this wasn't changed the last time since the MASS guys did not find any error for this in the ECU. Maybe it was the O2 sensor.

I thought it would be normal procedure to replace the O2 sensor every time a major work is done on the catalytic converter. Since yours has been replaced altogether, I am surprised the MASS did not replace the sensor inspite of having known it is faulty.
A properly working and calibrated O2 sensor is required if the cat con is to do what it is required to do.

[R2D2]

Originally Posted by TheMileCruncher

I got the battery load tested over the weekend from a local store and the battery is absolutely fine. Then I checked the alternator by disconnecting the negative battery terminal while the engine was running and did not notice any changes in the idle RPM.

Please never disconnect the battery when the car is running. It can fry your car's electronics mainly the ECU. If you want to test the alternator there are other ways to do it.

[TheMileCruncher]

Originally Posted by SCORPION

I thought it would be normal procedure to replace the O2 sensor every time a major work is done on the catalytic converter. Since yours has been replaced altogether, I am surprised the MASS did not replace the sensor inspite of having known it is faulty.
A properly working and calibrated O2 sensor is required if the cat con is to do what it is required to do.

This was the first time I've ever faced an issue with the cat con on any of my cars so I have no idea about this. I think I'll reconfirm this with my service adviser the next time I visit them.

Originally Posted by R2D2

Please never disconnect the battery when the car is running. It can fry your car's electronics mainly the ECU. If you want to test the alternator there are other ways to do it.

I wasn't aware of this. I've seen a lot of mechanics do this in the past (once on my Optra too) and hence tried this out. Thanks for cautioning me, I'll keep that in mind now.

[TheMileCruncher]

Update: I got the wiring for the accessories (fog lamp, remote locking and secondary horn) replaced which were chewed off by the rat. We reconnected all the accessories and tested the car for a few minutes, everything seemed to be working fine.

An hour later, I noticed that the car was jerking a bit while accelerating in the first couple of gears so I started my own troubleshooting by disconnecting the secondary horn and the jerking disappeared.

The following day, I was en route to a hill station for a weekend getaway when I noticed that with the A/C ON, the idle RPM would keep fluctuating between 400-1000 and the car would almost stall.

This time, I went ahead and disconnected the fog lamps wired to the battery using a 5 pin relay. As I was hoping, the fluctuation disappeared completely and I did not encounter any other issues during the 2 day trip.

Yesterday however, after refilling CNG at a newly opened outlet, I started encountering the same RPM fluctuations. This time however, the RPM would drop down (to less than 500) only while coming to a halt and then steady itself at idle. At times, the car would even stall.

I've now disconnected all accessories from the battery and hope this will resolve the issue. If not, I don't know what to do next.

[R2D2]

Originally Posted by TheMileCruncher

I wasn't aware of this. I've seen a lot of mechanics do this in the past (once on my Optra too) and hence tried this out. Thanks for cautioning me, I'll keep that in mind now.

Well, TBH, FNG mechanics aren't the last word in technical knowledge or capabilities. Many of those kids are also learning at your expense. I speak from personal experience going back decades. Which is why I prefer ASCs to FNGs even if the former's services come at a premium.

Originally Posted by TheMileCruncher

I've now disconnected all accessories from the battery and hope this will resolve the issue. If not, I don't know what to do next.

Rat bite? You need to get the entire harness checked and then add back your accessories one by one till you find the engine misbehaving. Then either disconnect that part permanently or replace it and the related wiring. A good automobile electrician or the MASS would help you.

[sumeethaldankar]

Does the Celerio have a drive by wire throttle system or a cable is attached to the accelerator? In case if it's a drive by wire see if the accelerator comes with any electric relay. Replace same and check.

[TheMileCruncher]

Originally Posted by sumeethaldankar

Does the Celerio have a drive by wire throttle system or a cable is attached to the accelerator? In case if it's a drive by wire see if the accelerator comes with any electric relay. Replace same and check.

Yes, it comes with an electronic throttle body. The MASS guys have checked the sensors, wiring harness and everything checked out.

Now with the accessories removed, I'm going to test the vehicle again. If the issue persists, I'll ask them to check this.

[sumeethaldankar]

Originally Posted by TheMileCruncher

Yes, it comes with an electronic throttle body. The MASS guys have checked the sensors, wiring harness and everything checked out.

Now with the accessories removed, I'm going to test the vehicle again. If the issue persists, I'll ask them to check this.

My Civic had a similar issue as described in this post.
It was touchwood resolved by replacing the relay. I would say change the relay and see once it's won't be a very expensive item.

[TheMileCruncher]

Originally Posted by sumeethaldankar

My Civic had a similar issue as described in this post.
It was touchwood resolved by replacing the relay. I would say change the relay and see once it's won't be a very expensive item.

Since you've encountered a similar problem which was resolved by this, I'll definitely give it a try.

[Chethan B G]

TBH, I wouldn't add tampered/repaired accessories that too when the car is going through unresolved issues.

Rat bites warrants for a complete harness check.

I get a feeling that the problem is getting complicated. I would prefer an ASC. 😊

[TheMileCruncher]

Originally Posted by Chethan B G

TBH, I wouldn't add tampered/repaired accessories that too when the car is going through unresolved issues.

Rat bites warrants for a complete harness check.

I get a feeling that the problem is getting complicated. I would prefer an ASC. 😊

All accessories were connected directly to the battery without taking any connections from the main harness and these were the wires that were chewed off.

The main wiring harness was not affected at all and the same was inspected a couple of days before the incident with the rat occurred.

As per the ASC, the wiring harness was working fine but I'm still going to get it checked again just in case.

As for the accessories, I am now running without any external accessories and the car worked fine all morning today except for once where the RPM dropped and came back steady again.

I plan on asking the ASC to install these accessories again by running a new wiring set as they had said that if done by them, this issue will be covered under the warranty. And yes, I always take my car to the ASC since I don't trust any local mechanic with my car.

[TheMileCruncher]

Update: So I ran the car without any accessories for a few days and continued to encounter the same problem. The RPM would start fluctuating at idle in stop and go traffic followed by rough idling. Once I shut off the engine and it cools down, the rough idling would vanish and the RPM would stay steady until the engine heats up again after driving for 15-20 minutes.

This time I was able to capture a short video of the issue I encounter (see below) and shared it with my service adviser at Vitesse (ASC).

http://youtu.be/pE_h5in5KHo

I left the car with the ASC for a couple of days thinking that this time around they will be able to help resolve this.

However, when I was called to meet with the service manager yesterday to discuss the issue, he told me that the issue is caused because I do not run the vehicle in petrol mode as I should which causes the tappet valves to not get enough lubrication.

He said that they poured petrol on the valves from the head and the car was idling fine for more than 45 minutes.

The solution as per him was that I should drive the car everyday in petrol mode for at least 15 kms even when the car manual says that I should drive the car for 5-10 kms in petrol after every 300 kms (I drive the car atleast 2-3 kms in petrol everyday in the morning).

When I asked him how to get rid of this issue permanently, his response was that there is no issue and if I drive the car in petrol everyday, there should be no issues at all.

I did not agree with him but I had to give him a chance so I took the car and left. This time, I drove the car in petrol mode only because I was sure that even in Petrol, the issue would reappear and that's what happened.

I called them back and the manager's response was "Surprising, this should not happen".

Now I'm stuck with a malfunctioning car and the ASC has no clue on how to resolve this.

Any ideas on how to resolve this?

BTW, I found someone else facing the exact same issue on another forum and he hasn't found a solution either for the past 1 year

Link: https://mechanics.stackexchange.com/...g-zero-voltage

[R2D2]

Have you had the wiring harness checked?

[TheMileCruncher]

Originally Posted by R2D2

Have you had the wiring harness checked?

Yes. No issues found with the harness as per the ASC.