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Car accelerating/engine revving on its own
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BryanL
New User
Oct 30, 2021, 6:50 PM
Post #1 of 5
(1999 views)
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Car accelerating/engine revving on its own
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This will be long, but please bear with me, I want to make sure people have all the facts and series of events. I just bought a 2002 Hyundia Accent last Wednesday. Last Saturday, after stopping and putting it in park, the engine revved up to about 4000 rpm and stayed there, I thought the pedal was stuck or something, but no. I turned the car off and called the dealer I bought it from and he said to bring it by. When I started the car back up, it was fine. On the highway, it seemed to surge a bit, lose speed while driving, feel like it was pushing through sludge for a second or two at a time.
When I got into the city and was stopped at a light, suddenly it starts trying to accelerate. I'm freaked out, I'm standing on the brakes trying to stop it from moving, it's grinding, trying to move forward. I finally manage to pull into a parking lot and put in park, the engine keeps revving up to 6, 7000 rpms before I shut the car off. Again, when I restarted it, it was fine.
I get it to the dealer, he opens the hood and has me press the gas while the car's turned off and while it's running, he says the throttle line is probably stuck. He sprays it with WD40 and we take it out on the highway and around the city, nothing happened, I think that must have been it. The whole week goes by with no issues, then last night, Friday, the car was doing that brief slowing thing again, when I parked at my house, engine revs to 4000 and stays there. Thinking its the throttle line like he told me, I pump the gas to try to free it up and the engine did go down to a normal idle and stay there.
But now I'm thinking, if this is an issue with a stuck throttle line, then what should be happening is the car staying at the speed I have it at and not slowing down when I take my foot off the gas...NOT accelerating or revving by itself from a full stop. So I do some searching online and see that all this matches effects of a bad idle control valve, because it happened when I was either stopped in traffic or after shifting into park. But everything I read said a bad idle control valve would cause the check engine light to come on, which it isn't. So I can't figure out what this is.
I know this was a really involved post, but hoping someone can help with what this issue is?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 30, 2021, 9:09 PM
Post #2 of 5
(1990 views)
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Re: Car accelerating/engine revving on its own
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Bryant! Can't you just take this back and go find something else? It's clearly a weapon on wheels to you and or others.
OMG, dealer just sprays it with WD-40 and sends you out to test it? Does it get worse than that anywhere?
T
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BryanL
New User
Oct 31, 2021, 5:45 AM
Post #3 of 5
(1974 views)
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Re: Car accelerating/engine revving on its own
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Take it back...why didn't I think of that. These types of forums *do* exist for a reason. 🙄
If I can have them fix it within the warranty period, I would rather do that, given the time and money I've already spent registering and insuring it.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 31, 2021, 6:27 AM
Post #4 of 5
(1966 views)
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Re: Car accelerating/engine revving on its own
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Understood. By the time and hassle of registering it, that $ is hard to impossible to recover and these dealers know that.
There are so many failsafe things for an engine to NOT run wild like you described IDK where to begin is why.
Return springs, electronic RPM limiters to name two.
Cables if used at all (many don't use cables) can fray and stick is why those are about gone long ago.
When a load is put on an engine like steering, A/C that compensates RPM loss so you don't know it really if gone all wrong IDK what could happen so add that to the list.
It shouldn't have been sold as usable in this shape no telling now what it's been thru to cause this or if worth fixing.
IDK is a viable answer for a forum vs being there in person!
I will venture one more thing (a wild guess) that can do this is unmetered air thru a leak for vehicles that use vacuum boosted power brakes. There should be a spot to hook up a line (metal) or hose for actual manifold vacuum past where any throttle plates are that goes on to a check valve and grommet at a vacuum booster to hold that vacuum when it's NOT available for a time. Anything wrong with any of those items wrecks that and can cause a wild idle.
That's why things are too much for the web and should be seen and absolutely fixed (no guessing) or removed from service on the road or junked for parts if it can't be known found and fixed -- this fits that is why,
Tom
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tractorboy
User
Nov 5, 2021, 5:57 PM
Post #5 of 5
(1889 views)
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Re: Car accelerating/engine revving on its own
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I had something like that happen to my La1 2003 Impala. Turned out it was the knock sensor. Think about it the knock sensor has a direct line to your timming, supposed to retard your timming when it detects irregular fuel detonation but if the knock sensor actually breaks i suppose it could do the opposit, which it did on my impala...random really high idle also at the same time i had trouble with my 4T65E trans PCS solenoid which would from a start cause the the car to sort of launch.
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