My car accelerates on its own....

[Oskee2001]

Hi everyone...this is my first post here, so please be kind! Anyway, I have some major problems with my 97 SC2, with 57,000 miles on it. Lately, it idles rough, and the rpms while idling shoot up to as much as 3000rpm before dying back down to about 800-1000. While driving it will do it as well, and you can imagine how dangerous that can be. it's gotten to where I have to put it in neutral at stoplights. Also, at the same time the rpm's are going crazy, the coolant temperature indicator is hopping all over the place.

Thoughts? I haven't had problems with the car before, and the oil has been changed regularly. in fact, it was just changed about a week ago, which is when everything got worse.

Thanks everyone...any help is appreciated!

[sierrap615]

this is probilly the common ECT problem, but could also be a sticking or carb'ed up IAC or EGR.

here is the link to the ECT repair - http://www.saturnfans.com/forums/showthread.php?t=24003

[mysatilac]

I'm assuming its an automatic since dropping into nuetral is new to you

from what you've said I would say almost definintly the ECTS (Engine Coolant Temperture Sensor)
your computer will adjust your throttle to compensate for the engine temperture, if this sensor is bad, it wont do the proper adjustments or it will do the wrong ones and you get a situation similar to what you've described

Cleaning the throttle body out wouldn't hurt either, the IAC (Idle Air Control) is located inside your throttle body, and will help out with your rough idle if the ECTS doesn't fix all your problems,

First post here huh?
Well, just as a tip listen to sierrap615 he knows what hes talking about

[Oskee2001]

Thanks everyone...took it to get a computer diagnostic yesterday, and it is indeed the ECT. The shop recommended a major tune up, including changing the ECT/Pig Tail. Their price for a tuneup involving new spark plugs, cables, valve cover gasket, and fuel filter: $490. This seem high to anyone?

[sierrap615]

most of that is labor i bet, they charge $95/hour here in chicago. none of those jobs couldn't be done by a home mechanic with some skill and the right tools.

[Oskee2001]

I'm in Chicago as well....can you recommend a good mechanic? I found that I can get the parts for about $100. The mechanic that gave me the original estimate said that it would only take him two hours to do the work. So it sounds to me like he might be price gouging me a bit...

[sierrap615]

as i'm told average mark-up on parts is commonly $100. sorry i can't recommend a mechanic, the only guy i would recommend only works on anitques and hot rods. besides that i do all my own work or go to the dealership. or if you want, i could do the work. i'm in tech school right now and don't charge much. PM me if you are interested

[Oskee2001]

So...i replaced the spark plugs, cables, ECTS, and put in a new valve cover gasket. but the car continues with a rough idle, although acceleration is back to normal. Any idea what might be causing this? the only thing i didn't do is change the fuel filter....would that be it?

And sierra, whereabout in chicago are you? I might have to take you up on your offer....

[mysatilac]

Originally Posted by sierrap615

this is probilly the common ECT problem, but could also be a sticking or carb'ed up IAC or EGR.

Yeah you might want to change out the fuel filter if it was recommended by the shop you took it to
Though I'd try cleaning your Thottle Body and IAC valve with carb cleaner first, cheap, easy, and always helps.

[Oskee2001]

Originally Posted by mysatilac

Yeah you might want to change out the fuel filter if it was recommended by the shop you took it to
Though I'd try cleaning your Thottle Body and IAC valve with carb cleaner first, cheap, easy, and always helps.

good call...the throttle body is where the intake is connected to, correct? and how would one go about cleaning it? sounds like its something I can do myself...

[mysatilac]

Yes, the throttle body is connected by two bolts (and your throttle cable, a vaccum line, and the two sensors wires) and is where the intake tube connects to your intake manifold. Be careful with the gasket when you remove the throttle body, also remove the IAC (idle air control) valve which is connected to the TB by two torx head screws, once it is out, spray the inside of the TB very well with carb cleaner while moving the throttle back and forth checking for binding and that it closes and opens all the way easily, then you want to spray down ithe IAC's pintle (the spring) and when satisfied that everything is clean and dry, reasemble reset your PCM by puling the - cable off your battery for ~5 minutes, then reconnect and fire it back up.
Hope this fixes your problem...

[sierrap615]

downers grove.

in many cases, the throttle body doesn't need removed to be cleaned. but on the other hand, you'll be suprized how thick the gunk is. the first time i took mine off i probilly took about 2 dozen Q-tips to it, at least. i'm funny like that, my throttle body has to be spot-less, but my bedroom on the other hand....

also i would rather pull the PCM B fuse instead of the neg cable. its faster, easier, safer, and you won't lose your radio presets.

[mysatilac]

I wouldn't clean one without taking it off, because if you leave it on you are just blowing carb cleaner and all that gunk down into your intake runners

Yeah, if it hasn't been cleaned, it is well workth it to take it off, there will be a large amount of carbon built up in there (normally not visible unless you look past the throttle plate into the back of it, or take it off)


You can pull your PCMB fuse, but still leave it out for ~5 minutes, to make sure it resets, some people say as few as 15 seconds. What you're doing here is clearing the computers memory, so that it re-learns how to control your car with the new/cleaned pieces, giving you better performance and fewer problems...

I'm not arguing, I'm agreeing (however it sounds)

BTW I just found a good site for smileys (duh)
www.emotipad.com

[Oskee2001]

how much do you suppose a shop would charge to do this? i'm sort of nervous about getting into a situation i won't know how to get out of.

[mysatilac]

Its not hard unless you make it hard, I dont know what a shop will charge you.
But the only thing you can really mess up is that gasket (between the TB and intake manifold)
And it is about $8-$15. But can normally be reused

The first time I did this I was suprised how easy it was! So I also bored my throttle body and knife edged the throttle plate. Big gains for a DIY

I have the utmost faith in you,
Repost in the middle of the job if you're having problems (very doubtful)