RE : Car accelerated while pressing brake pedal - Kia Forum
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post #1 of 13 (permalink) Old 01-25-2011, 02:21 AM Thread Starter
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Default RE : Car accelerated while pressing brake pedal

I have a Naza Sorento EX model 2.5 diesel bought in July 2010. When I release pressing the accelerator and slow down the car say coming to a traffic light junction (engine rpm is down to about 950-1000 rpm), the car engine is accelearted to about 1,200 rpm while I press on the brake pedal. I have to press hard on the brake pedal to keep the car stand still and the engine is still running at about
1,200 rpm.

This problem does not occur very often. Sometime, once in 2 weeks
or even in 2 months.

I have send the car back to the service center to rectify
the problem but not solved.

Anybody encounter this problem ? Please advise.

VK Liew
25/01/2011

Last edited by VKLIEW; 01-25-2011 at 03:35 AM.
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post #2 of 13 (permalink) Old 01-25-2011, 03:05 PM
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Originally Posted by VKLIEW View Post
I have a Naza Sorento EX model 2.5 diesel bought in July 2010. When I release pressing the accelerator and slow down the car say coming to a traffic light junction (engine rpm is down to about 950-1000 rpm), the car engine is accelearted to about 1,200 rpm while I press on the brake pedal. I have to press hard on the brake pedal to keep the car stand still and the engine is still running at about
1,200 rpm.

This problem does not occur very often. Sometime, once in 2 weeks
or even in 2 months.

I have send the car back to the service center to rectify
the problem but not solved.

Anybody encounter this problem ? Please advise.

VK Liew
25/01/2011
Well a typical DEISEL does not run on vacuum. So most diesels need a outside VAC source to run brakes and such. On a typical GAS/Petrol eng a bad brake booster or check valve or a simple VAC leak would back feed the intake and make idle jump accordingly yes. With the diesel you have, you need to look as well at the Brake Booster which sounds like your area of problem for the jump idle at stop lights. But it as well can be anything in this case that tied into the VAC generator system to run anything on this deisel vech that a normal GAS/Petrol vech would never have had. Something is telling the injection pump more air then what is, is going into the eng and it is dumping more fuel for that. And that starts the circle of run away deisel engine RPMS. That is why if you do not shut the fuel off to a deisel eng it will run forever till you do. Which is a classic law of physics at its best. Much like a COAL fired boiler on a train or a wood bonfire on the beach.
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post #3 of 13 (permalink) Old 01-25-2011, 09:04 PM
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I know this sounds stupid but when I used to drive my friends car wearing work boots my foot would occasionally hit the accelerator when braking. At the time I did not know what the reason for the engine acceleration was. I mentioned it to him and he said it had happened to him a few times just as you described. It was not until it happened to our other friend that the issue was diagnosed.
It may be and unlikely cause but it is worth paying attention to, next time it happens take note of the position of you foot on the brake pedal.
good luck
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post #4 of 13 (permalink) Old 01-25-2011, 09:13 PM
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Remembering my 1978 diesel Rabbit that ran away several times with a great roaring, dense black smoke and high speeds. No response to turning the switch off. Couldn't stop it with the brakes until a long uphill slowed it somewhat--then it suddenly acted normal. They didn't do it new but after 30-40,000 mi. it could happen.

There were several serious accidents in this area. In one, a lady was killed when her Rabbit flipped over on a downhill after she sideswiped several cars and a stretch of roadside railing trying to stop.

VW decided that crankcase oil was being sucked in through the PCV system and issued a little plastic baffle to install under the valve cover. It worked. The 79 and later diesels came with this 'fix' installed.

We do not have diesel KIAS in the US, but I wonder if a similar thing is happening?

We're in a giant car heading towards a brick wall and everyone's arguing over where they're going to sit.
David Suzuki

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post #5 of 13 (permalink) Old 01-25-2011, 10:08 PM Thread Starter
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Dear 04SorentoLX,

Thank you for your invaluable info. I will share this info with the technician. Can
you a little bit more specific what the technician need to do to rectify this problem.

Thanks a lot.

VKLIEW
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post #6 of 13 (permalink) Old 01-25-2011, 10:11 PM Thread Starter
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Thank you guy. I am very sure I did not step on the accelerator while pressing on
the brake pedal.

VKLIEW
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post #7 of 13 (permalink) Old 01-26-2011, 05:28 PM
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Originally Posted by VKLIEW View Post
Dear 04SorentoLX,

Thank you for your invaluable info. I will share this info with the technician. Can
you a little bit more specific what the technician need to do to rectify this problem.

Thanks a lot.

VKLIEW
VKLIEW franx brought up a very good point too. Engine oil and diesel fuel are very similar to a diesel engine and it does not care which it gets to run on. Which in a way if the flip side of what I was saying to you. Extra fuel what ever form it comes in will take the air that is always going in and run on it unrestricted. Hense a higher then normal idle. Or runaway engine RPM's. In your case to answer what you asked of me sorry I can not be more specific for you. As there is no way to tell sitting here with out the car in front of us what is or is not hooked up to the VAC generateing source (VAC pump). If anyone of many thing that can be, is defective or gone bad eiter directly or its check (one way) valve. It can give the engine more air then the ECM thinks was going in as per normal idle. And then it with these electronic fuel injection vechs these days will step up the injector pulse rate to burn it in error and this gives you the higher idle. I would start with the brakes first as that is when you get the worst engine idle boost and kick up. But it can be anything really that just happens to just do it when you push the brake pedal is all. But a very good start is check valves and brake booster and hoses area. If the mech you are useing can not take this info and run with it. And track it down like one should be able to. Then I am afraid you maybe are not in the right place to be getting this vech fixed. And yes many mech sadly thou they say they are and do, are not one. And have no diagnostic skill at all.

ADDED HINT: Cruise control is controlled in many ways by brake pedal too. And it has both VAC and engine idle governing jobs too if you think slowly about it and how it works.
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post #8 of 13 (permalink) Old 02-14-2011, 01:52 AM Thread Starter
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04SorentoLX, TQVW, I had send my Sorento to the service centre and left it there for 4 days to check up. Technician confirmed that the vehicle was in order. He suspected that the problem was due to Accelerator Position Sensor (APS) as it had been shifted to the left that is a Left Foot Accelerator due to my physical disability. (APS socket, 6 wires was cut and extended by about 18 inches.) Now, the technician opined that electronic signal stability was affected due to the lengthen wire. When the vehicle was scanned, the error code appeared indicated there was a problem with APS.
The reasons given were, when the brake pedal is pressed, vacuum in the brake booster was used up and the alternator started to generate more air that lead to the runaway engine RPM's because signal from the APS was not transmitted properly to the ECM etc. (something likes this). 04SorentoLX, what do you think ? Is the lengthen wire cause all the problem ?

VKLIEW (14/02/2011)
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post #9 of 13 (permalink) Old 02-14-2011, 12:16 PM
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04SorentoLX, TQVW, I had send my Sorento to the service centre and left it there for 4 days to check up. Technician confirmed that the vehicle was in order. He suspected that the problem was due to Accelerator Position Sensor (APS) as it had been shifted to the left that is a Left Foot Accelerator due to my physical disability. (APS socket, 6 wires was cut and extended by about 18 inches.) Now, the technician opined that electronic signal stability was affected due to the lengthen wire. When the vehicle was scanned, the error code appeared indicated there was a problem with APS.
The reasons given were, when the brake pedal is pressed, vacuum in the brake booster was used up and the alternator started to generate more air that lead to the runaway engine RPM's because signal from the APS was not transmitted properly to the ECM etc. (something likes this). 04SorentoLX, what do you think ? Is the lengthen wire cause all the problem ?

VKLIEW (14/02/2011)
Yes it could and this gets into the last part of what I said. Something is kicking up the idle over normal. And if this retro fit messed with ASP as you call it for the diesel fly by wire throttle is getting bad signals it will or can tell the diesel injection to kick up its game. As if it were telling a engine that was running at 750rpm normally to do so when it goes down to 500rpms. But in your case it onlys SEE's and is told that, but that is not for real. But it still kicked it up and you get not 500 to 750rpm's again but 750 to 1000-1200rpm's now. I blind and hard of hearing man can be told there is no traffic when there is, and he will walk out into it and get hit from the bad info.

Last edited by 04SorentoLX; 02-14-2011 at 12:20 PM.
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post #10 of 13 (permalink) Old 02-16-2011, 02:11 AM Thread Starter
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04SorentoLX, Any suggested solution to increase the electronic signal
via the cable ?
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