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-   -   2005 5.7L accelerates by itself out of control? (http://www.jeepgarage.org/f181/2005-5-7l-accelerates-by-itself-out-of-control-34410.html)

oldgeezer 01-20-2012 03:52 PM

2005 5.7L accelerates by itself out of control?
 
What seems to be a major problem. Start the jeep , put in drive and truck accelerates on its own without foot on pedal. Pedal is near floor and continues to accelerate. Need to slam on brake, put in reverse, and then park. Vehicles still is "racing" wildly. Shut down by turning off. Did the ETC go "crazy"??? Has anyone experienced this? Is it safe to drive? When I started the vehicle to drive a short distance, everthing was back to normal. Any ideas please? Thanks.

dr.lee.baugh 01-20-2012 04:24 PM

Re: 2005 5.7L accelerates by itself out of control?
 
First I've heard about the ETC acting up like that.



What sort of RPMs are we talking about when it is "racing wildly"?


When cold, the vehicle will raise the idle RPM a few hundred and it will be more likely to creep forward on you during this time - but that certainly doesn't explain what you are describing!


Any DTC's? Did the ETC warning light come on at all? Usually, this system is pretty good at picking up a minor problem before it becomes a major one (like you describe).

Another COMMON cause of this sort of incident in the winter months (not saying that's what happened, but I have seen a fair number of people coming in from accidents with this as the cause) is driving while wearing winter boots. People inadvertently hit the gas and the break, and can't feel that they are doing it because they get no feedback from the pedals...

nyc_medic 01-20-2012 04:27 PM

Re: 2005 5.7L accelerates by itself out of control?
 
I wouldnt drive it like that. Check to make sure that the gas pedal moves freely and that it doesnt bind. Good luck

SvenskaJeepGuy 01-20-2012 04:53 PM

Re: 2005 5.7L accelerates by itself out of control?
 
crazy! this is the first i have ever heard of this problem. what kind of speeds and rpms are you having?

2005JGC 01-20-2012 05:55 PM

Re: 2005 5.7L accelerates by itself out of control?
 
There are so many fail safes to this, there may be 1 in a million or even a billion reasons how it could allow this without the actual throttle pedal input (none that I know but I am sure there will be stars that align for someone some how. There are 2 accelerator pedal positions sensors and 2 throttle position sensors. If ANY one of the 4 sensors doesn't jive with the others it will make it stupid and you will lose all control of the throttle (etc and traction control lights will likely illuminate) which normal spring loaded position for the throttle plate is nearly closed so its not like it will shut off power and leave the throttle plate wide open.

All of that to say inspect your throttle pedal, make sure you don't have a floor mat that its stuck in , you would be surprised how often people complain of something similar and they have their slush mats stacked on their floor mats or similar. Make sure you have the whole throttle pedal travel and go from there.

FlyinRyan 01-20-2012 05:58 PM

Re: 2005 5.7L accelerates by itself out of control?
 
bad accelerator input sensor or throttle body is my guess.

Blueflame1979 01-21-2012 03:18 AM

Re: 2005 5.7L accelerates by itself out of control?
 
It can be a sensor, my throttle position went bad way before the computer threw on a check engine light. My Jeep would lunge forward ir backwards depending on which direction I was going when I gave it little gas. It used to rev up on its own, rpms used to go crazy and a month before it threw the check engine light, it started stalling on me at lights. I went through the whole checklist, checked winter boots, floormats, was making sure If I'd be braking had my foot solid in the brakes and not the gas pedal at the same time. Went to the Dealer and told them about it the tech tried to replicate the problem but couldn't, so they just looked at me like if I were crazy. Finally it threw the check engine light and a shop knew exactly what it was and when they replaced the tps it didn't do it anymore. I would advise you not to drive like that since I almost in a couple of accidents because the tps was giving out, but I did drive carefully. I went 4 months with this issue and no shop or dealer had a clue on what it was and blamed it on driver error, before it threw the code. Keep us posted good luck with that.

2005JGC 01-21-2012 03:27 AM

Re: 2005 5.7L accelerates by itself out of control?
 
4.7l is very different from the hemi and has only 1 tps, as I stated the Hemi (fly by wire) has 2 redundant sensors that read 2 different voltages that must jive or it goes stupid. Again as I already stated there are also 2 redundant accelerator pedal position sensors (what the pcm uses to deturmine how much to open the throttle body). If ANY of those 4 signals isn't within set parameters of each other then the whole system goes dumb. If one accelerator pedal sensor is reading full throttle and the other is reading 1/3 throttle meanwhile the throttle blade is currently at about 1/3 throttle, the system goes dumb, if a throttle position sensor sees the blade as 3/4 open and the other is reading at 1/5 open and the accelerator pedal is at 3/4 throttle , the system goes dumb. Its is about as different as you can possibly get from how the 4.7l operates while performing the same basic function. These redundant sensors are there to prevent runaway vehicles, for safety, it would rather the vehicle go dumb than run a tank out of control down the road.

btw, the 4.7l tps is SUPER common (if you search for 4.7l idle concerns on the forum you will see I have commented on a great many of them and suggested the tps was the first place they look... Meanwhile I have personally only seen a handful of throttle bodies get replaced (the tps sensors on the 5.7l throttle body are internal) and have never replaced one myself.

I am not saying there is no way possible its not the throttle body, or the accelerator pedal assembly (where the sensors are) it could be, I'm just talking odds here... and on the interwebz when I don't have a car infront of me, I dont have a witech and scan data, no data logging the events, it is simply a game of odds.

If you check out what I have suggested and it persists I do highly suggest you get it into a shop to be looked at (dare I suggest a dealer?).

Blueflame1979 01-21-2012 03:54 AM

Re: 2005 5.7L accelerates by itself out of control?
 
Quote:

Originally Posted by 2005JGC (Post 557272)
4.7l is very different from the hemi and has only 1 tps, as I stated the Hemi (fly by wire) has 2 redundant sensors that read 2 different voltages that must jive or it goes stupid. Again as I already stated there are also 2 redundant accelerator pedal position sensors (what the pcm uses to deturmine how much to open the throttle body). If ANY of those 4 signals isn't within set parameters of each other then the whole system goes dumb. If one accelerator pedal sensor is reading full throttle and the other is reading 1/3 throttle meanwhile the throttle blade is currently at about 1/3 throttle, the system goes dumb, if a throttle position sensor sees the blade as 3/4 open and the other is reading at 1/5 open and the accelerator pedal is at 3/4 throttle , the system goes dumb. Its is about as different as you can possibly get from how the 4.7l operates while performing the same basic function. These redundant sensors are there to prevent runaway vehicles, for safety, it would rather the vehicle go dumb than run a tank out of control down the road.

btw, the 4.7l tps is SUPER common (if you search for 4.7l idle concerns on the forum you will see I have commented on a great many of them and suggested the tps was the first place they look... Meanwhile I have personally only seen a handful of throttle bodies get replaced (the tps sensors on the 5.7l throttle body are internal) and have never replaced one myself.

I am not saying there is no way possible its not the throttle body, or the accelerator pedal assembly (where the sensors are) it could be, I'm just talking odds here... and on the interwebz when I don't have a car infront of me, I dont have a witech and scan data, no data logging the events, it is simply a game of odds.

If you check out what I have suggested and it persists I do highly suggest you get it into a shop to be looked at (dare I suggest a dealer?).

you have said, you have stated, but you forgot to mention that I never compared my 4.7 to his Hemi, I was giving my opinion based on my experience rather than a diagnosis. I wish I would have stumbled upon ur on your posts about the tps, but I didn't and I learned through many headaches. By what you wrote, You sound like you know what ur talking about and I'm not here to argue that. In the end its going to be his decision to make wether ur right or ur wrong I Just want want to make it known where I'm coming from. I know this is not the time or the place but maybe u can help me out with something that has me stumped.

2005JGC 01-21-2012 04:10 AM

Quote:

Originally Posted by Blueflame1979 (Post 557278)
you have said, you have stated, but you forgot to mention that I never compared my 4.7 to his Hemi, I was giving my opinion based on my experience rather than a diagnosis. I wish I would have stumbled upon ur on your posts about the tps, but I didn't and I learned through many headaches. By what you wrote, You sound like you know what ur talking about and I'm not here to argue that. In the end its going to be his decision to make wether ur right or ur wrong I Just want want to make it known where I'm coming from. I know this is not the time or the place but maybe u can help me out with something that has me stumped.

Im here to help, and as I stated interwebz automotive diagnostics is fuzzy business, no one man is going to pinpoint the problem and be right all the time. I am not trying to scare anyone out of offering suggestions, the more the better, I was just trying to share simple info on how it operates.

Oh and feel free to ask for help if ya ever need it!

Sent from my SCH-I500 using Tapatalk

Blueflame1979 01-21-2012 05:00 AM

Re: 2005 5.7L accelerates by itself out of control?
 
Thanx man! , I was trying to help like everyone's been helping me here, So I thought with the little knowledge I have I was able to give back. I was hoping I was able to express myself without sounding rude. You broke it Down though, you gave us the run down on a hemi as far as those sensors go, it's rather interesting. Check ur pm. But enough about me let's get back to the issue at hand.

oldgeezer 01-21-2012 12:19 PM

Re: 2005 5.7L accelerates by itself out of control?
 
It seems that there have been a number of well documented similar instances in the mid to late 90's Grand Cherokees.
http://en.wikipedia.org/wiki/Sudden_...d_acceleration
Within the article, it was noted that the problem as I described was similarily caused by unintended electrical current in the cruise contol system that caused the throttle to open to WOT. Not saying that happened, but just another possibility. Where to go from here? Just live with the possibility I guess and be prepared for anything to happen. Thanks for all suggestions. Appreciated here.


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