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Old 26th November 2012, 20:32   #1
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Unhappy Random power drop

Hey guys,

Off late i have been having a very weird problem with my Elantra of random power loss.

This is what happened on my last trip. I left home at 6.30 AM and traveled about 35 KM and stopped for breakfast for about 30 mins, then when i started again everything was fine for another 5kms, then there was a sudden drop in the cars acceleration and then i noticed that the car would just not go above 2700 rpm no matter how hard i press down on the accelerator in any gear. So i stopped over and shifted to neutral but then again same thing the car would just not go above 2700 rpm. There was no engine check light or anything. i even checked the temp it was just below half mark(its usual position). I called my SA in the service station and he told me remove the battery cable and re-connect it and try again. i did that but still no luck. So he told me to bring it to the service station when i was free and that it was safe to continue as the temp was normal and engine check light was not on. I went on with my trip with the rpm not going above 2700. The car was still able to do some decent three digit speeds even in this condition. Then i reached my destination which was another 105 kms away and turned the car off for about 1 hour or so then started it again and everything in the car was back to normal and i drove back the entire 140kms without any problem. I went to the service station and tried to get it checked but there were no error codes recorded and the car is running fine now. My SA advised me to get the car in again when the issue occurs without switching off the car.

This is the 4th time i am facing this issue in the last 5 months and i have not been able to track the issue. Any help in this regard is highly appreciated.

Below are the details of the car.

CAR: Hyundai Elantra CRDI
Model year: 2006
ODO: 78000
OIL: Fully synthetic Shell Helix engine oil being used
Regularly serviced at Hyundai Authorised service station.



MODS: Did not find any thread with this specific power loss issue for CRDI Elantra. Please merge with other thread if it already exists.

Regards,
Rocky
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Old 26th November 2012, 21:19   #2
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Default re: Random power drop in Hyundai Elantra CRDi

Going by what you've detailed, it appears that the rpm is being electronically restricted at times. You can rev up to 2700 rpm in any gear without power loss, but then, cannot exceed 2700 rpm in any gear or even in neutral.

First thought that comes to mind: fuel quality / partial fuel flow restriction. What pump do you fill from when this happens? What was the last time you had your diesel tank and suction end filter cleaned?

Does the Elantra come with a mass airflow (MAF) sensor? Any sensors on the exhaust side, sensing diesel particulates? Either of these sensors having an electrical loose contact may not throw up an error code.

Or too much diesel particulate in the exhaust may also cause this. Exhaust system carbon deposit could be a culprit.

Is this a BS-III or BS-II vehicle (I would think BS-III)? I guess you might need to ask at your HASS.
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Old 26th November 2012, 21:21   #3
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Default re: Random power drop in Hyundai Elantra CRDi

Surprising the ECU has not found any error codes and was fine from the point of the ECU.

Is there anything to do with the sensor with the accelerator pedal?
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Old 26th November 2012, 21:30   #4
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Default re: Random power drop in Hyundai Elantra CRDi

Check out the fuel pump, mostly it's giving up. Had a similar problem on my Accent but it was petrol Accent. Just get the Fuel Pump or Fuel Pressure Regulator checked.
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Old 26th November 2012, 21:31   #5
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Default re: Random power drop in Hyundai Elantra CRDi

As SS-Traveller said, the rpm is being electronically restricted by the ECU. In other words, the ECU is going into Limp-home mode. In India, such cases on Hyundai diesels are mostly caused by a faulty EGR (Exhaust Gas Recirculation valve) or a faulty throttle position sensor.
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Old 26th November 2012, 21:34   #6
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Quote:
Originally Posted by SS-Traveller View Post

First thought that comes to mind: fuel quality / partial fuel flow restriction. What pump do you fill from when this happens? What was the last time you had your diesel tank and suction end filter cleaned?

Does the Elantra come with a mass airflow (MAF) sensor? Any sensors on the exhaust side, sensing diesel particulates? Either of these sensors having an electrical loose contact may not throw up an error code.

Or too much diesel particulate in the exhaust may also cause this. Exhaust system carbon deposit could be a culprit.

Is this a BS-III or BS-II vehicle (I would think BS-III)? I guess you might need to ask at your HASS.
I had filled up fuel in my regular petrol pump in Bangalore. The last time i complained about this issue my SA had got the MAF sensor cleaned about 2 months ago. I have no idea about any sensor in the exhaust system, i will check with my SA.

Thanks for the suggestion, now that you mentioned it i have been noticing black soot on my garage wall, but wouldn't this issue cause a consistent power loss as against random, however i will try and get the exhaust system cleaned once (any suggestion on how to get the catalytic converter cleaned as in the A.S.S they would suggest for a replacement).

It is a BS 3 vehicle.

My SA thinks it might be any issue with the fuel temp sensor based on my feedback any thoughts on this? (he is yet to see the car when the symptoms occur, funny thing it never occurs when i go to the service station).

Regards,
Rocky

MODS: sorry about the back to back post seem to be having some trouble with my login id.

Quote:
Originally Posted by predatorwheelz View Post
As SS-Traveller said, the rpm is being electronically restricted by the ECU. In other words, the ECU is going into Limp-home mode. In India, such cases on Hyundai diesels are mostly caused by a faulty EGR (Exhaust Gas Recirculation valve) or a faulty throttle position sensor.
If the ECU restricts the engine rpm and goes to limp mode due to the above reasons, wouldn't the ECU have an error code recorded.

Quote:
Originally Posted by saurabhkum View Post
Check out the fuel pump, mostly it's giving up. Had a similar problem on my Accent but it was petrol Accent. Just get the Fuel Pump or Fuel Pressure Regulator checked.
Will suggest this to my SA, but again if there is a drop in rail pressure due to faulty pump wouldn't the ECU record the error code for this. I had seen a similar error recorded when one of my injector cables has come loose (Code was something like Low rail pressure with cylinder or injector number)

Thanks,
Rocky

Last edited by Technocrat : 26th November 2012 at 23:29. Reason: Back to back posts merged.
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Old 26th November 2012, 21:56   #7
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Default re: Random power drop in Hyundai Elantra CRDi

Quote:
Originally Posted by rocky080 View Post
If the ECU restricts the engine rpm and goes to limp mode due to the above reasons, wouldn't the ECU have an error code recorded.

Will suggest this to my SA, but again if there is a drop in rail pressure due to faulty pump wouldn't the ECU record the error code for this. I had seen a similar error recorded when one of my injector cables has come loose (Code was something like Low rail pressure with cylinder or injector number)

Thanks,
Rocky
Yes for the above two problems the ECU will record the error code.

How is the car now during usage?

Anurag.
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Old 26th November 2012, 21:58   #8
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Default re: Random power drop in Hyundai Elantra CRDi

Although this sounds a LOT like limp-home, isnt 2700 rpm a bit too high for that?
It seems abit too high even on a petrol, let alone diesel.
My cars limp home is about 1-1.4k.
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Old 26th November 2012, 22:02   #9
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Default re: Random power drop in Hyundai Elantra CRDi

Quote:
Originally Posted by rocky080 View Post
...i have been noticing black soot on my garage wall, but wouldn't this issue cause a consistent power loss as against random...
ECU reads a choked exhaust as too much fuel, and cuts out supply beyond a certain RPM - but this might depend on quality of fuel at times. You might want to try a diesel additive like System-D before opening up things.
Quote:
get the exhaust system cleaned once (any suggestion on how to get the catalytic converter cleaned as in the A.S.S they would suggest for a replacement).
Usual practice by ASCs is to shove a high pressure water hose into the tailpipe for a few seconds, rev and throw the water out, repeat the process a few times.
Quote:
My SA thinks it might be any issue with the fuel temp sensor based on my feedback any thoughts on this?
Unlikely in a place with moderate temperatures like Bangalore.
Quote:
Originally Posted by rocky080 View Post
If the ECU restricts the engine rpm and goes to limp mode due to the above reasons, wouldn't the ECU have an error code recorded.
Always. And limp home mode will restrict RPM to 1200-1500, not 2700. Seems to indicate the ECU is getting some kind of unwanted feedback from some sensor and cutting fuel supply after 2700 rpm - but the feedback appears "normal" to the ECU.
Quote:
...if there is a drop in rail pressure due to faulty pump wouldn't the ECU record the error code for this. I had seen a similar error recorded when one of my injector cables has come loose (Code was something like Low rail pressure with cylinder or injector number)
Both too-high or too-low rail pressure will throw up error codes.
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Old 26th November 2012, 22:03   #10
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Default re: Random power drop in Hyundai Elantra CRDi

Quote:
Originally Posted by a4anurag View Post
Yes for the above two problems the ECU will record the error code.

How is the car now during usage?
The car is running perfectly fine now, it was also fine on my return journey when this issue occured.

Anurag.
Quote:
Originally Posted by mayankk View Post
Although this sounds a LOT like limp-home, isnt 2700 rpm a bit too high for that?
It seems abit too high even on a petrol, let alone diesel.
My cars limp home is about 1-1.4k.
This is my thought exactly. Also, if the car switches to limp home mode wouldn't the engine check light come, which did not happen in my case.

Regards,

Rocky

EDIT:



Quote:
Originally Posted by SS-Traveller View Post
ECU reads a choked exhaust as too much fuel, and cuts out supply beyond a certain RPM - but this might depend on quality of fuel at times. You might want to try a diesel additive like System-D before opening up things.
I use System D on a regular basis every alternate full tank, i use 1 ml with every liter of diesel.

Last edited by rocky080 : 26th November 2012 at 22:14.
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Old 26th November 2012, 22:08   #11
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Default re: Random power drop in Hyundai Elantra CRDi

Quote:
Originally Posted by SS-Traveller View Post
ECU reads a choked exhaust as too much fuel, and cuts out supply beyond a certain RPM - but this might depend on quality of fuel at times. You might want to try a diesel additive like System-D before opening up things.

Usual practice by ASCs is to shove a high pressure water hose into the tailpipe for a few seconds, rev and throw the water out, repeat the process a few times.
1)Just a noob doubt and sorry for asking if the ECU reads a choked exhaust then it should have problems during starting or idling also. Right?

Can't revving the engine clear up the exhaust?

2) Shoving a high pressure water hose into the tail pipe isn't that going to kill the engine? Will the engine be able to start with the water in the exhaust? This technique is new to me

Anurag.
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Old 26th November 2012, 22:55   #12
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Default re: Random power drop in Hyundai Elantra CRDi

Quote:
Originally Posted by a4anurag View Post
1)Just a noob doubt and sorry for asking if the ECU reads a choked exhaust then it should have problems during starting or idling also. Right?
Not choked - there may be a diesel particulate sensor, which cuts fuel at higher rpm because the ECU thinks the car is polluting more than normal. IIRC the sensor is present in BS3/Euro-III vehicles, not in Euro-II ones.

Quote:
Can't revving the engine clear up the exhaust?
Probably does - which is why the problem probably goes away after a high-speed high-rpm run.
Quote:
2) Shoving a high pressure water hose into the tail pipe isn't that going to kill the engine? Will the engine be able to start with the water in the exhaust? This technique is new to me
LOL - ask the HyundaiASS and TATA-A$$ guys - they all do it! Won't flood the engine if the hose is applied for just a few seconds. Yes, the engine does start, and pours out a very black solution! Keep your distance from it, don't get it on your clothes, or the best dry-cleaners won't be able to do much later on!

Last edited by SS-Traveller : 26th November 2012 at 23:12.
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Old 26th November 2012, 23:09   #13
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Default re: Random power drop in Hyundai Elantra CRDi

Quote:
Originally Posted by rocky080 View Post
Hey guys,

Off late i have been having a very weird problem with my Elantra of random power loss… for CRDI Elantra. Please merge with other thread if it already exists.
Check for turbo failure as well.
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Old 26th November 2012, 23:14   #14
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Default re: Random power drop in Hyundai Elantra CRDi

Quote:
Originally Posted by mustysekhon View Post
Check for turbo failure as well.
Turbo failure will produce heavy smoke on revving, and refusal to deliver power under load. OP says he can do 3-digit speeds effortlessly till 2700rpm, so turbo failure can be ruled out.
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Old 26th November 2012, 23:17   #15
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For how long did you disconnect the battery?
15 minutes, and a couple of dabs on brakes seems ideal. I've occasionally not got a reset with quick jobs.
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