Car automatically accelerates

[whitesmoke]

My car has been acting weird lately. It starts up good and idels around 1k rpms but after ive been driving or letting it sit and idel, the rpms raise to 2,500-3,500 rpms. Sometimes when I'm driving and at a stoplight the idel will go up and when I put it in gear it will accelerate on it's own. Alsi when this starts to occur is wen im driving and i press my clutch in the rpms shoot up to 3,500 rpms and stay there. Any ideas on what would cause this will help.

I have 95 talon with a 6 bolt swap.

 

[PanZero]

Idle speed control motor?

 

[whitesmoke]

Is there a way I can test to see if that's it. Sorry if that sounds dumb Ive never a problem like this before

 

[SleepinGVR4]

Just unplug it.

 

[WeaselHack]

Just unplug it.

Yeah because that's a proper testing procedure that will tell you NOTHING!

DmTaLoN's Idle Speed Control Test/Fix Page! <-- ISC Testing Procedure

 

[GIRman67]

Try going to an autoparts store. Lots of them rent out ODB2 scanners if it shows a bad ISC, then there is your answer. If you have a multimeter handy try testing the resistance between 1-2, 2-3, 4-5, 5-6, each should read 30ohms if they read differently your ISC is bad.

EDIT: beat me too it

 

[whitesmoke]

Thanks for the info. I'm guessing that's it. I checked the throttle body to see if it was sticking but that wasn't it.

 

[Gysgt Guy]

I would recommend taking the battery out for that test as well...its just a pain in the ass trying to get the volt meter leads on those little pins!

 

[gusu]

I doubt the ISC would do that. As the ISC functions with the ECU. That is why you must unplug things from the ECU to adjust the BISS.

Your ISC basically actuates when it reads a certain RPM from the ECU.

That is why the ISC motor is more likely to not work at idle and under deceleration only.

I'm not totally convinced your issue would be electrical. To me it seems more of a clutch engagement problem. Are you having any problems shifting?

It may also be a ECU problem, but I'm not sure because from what I've read on all the information I've read when fixing my idle did not make the car accelerate on its own in gear. Unless you mean with the clutch pushed in.

The only thing I kind of skimmed over because it wasn't highly relevant to the issue I had, was the CAS but from what I did read I'm not totally sure that could be the issue.

So check your ECU and let us know if you have any issues with certain gears like 5th/reverse or 1st gear.

 

[Absit]

Check your throttle cable tension, it's probably too tight.

 

[Gysgt Guy]

I doubt the ISC would do that. As the ISC functions with the ECU. That is why you must unplug things from the ECU to adjust the BISS.

Your ISC basically actuates when it reads a certain RPM from the ECU.

That is why the ISC motor is more likely to not work at idle and under deceleration only.

I'm not totally convinced your issue would be electrical. To me it seems more of a clutch engagement problem. Are you having any problems shifting?

It may also be a ECU problem, but I'm not sure because from what I've read on all the information I've read when fixing my idle did not make the car accelerate on its own in gear. Unless you mean with the clutch pushed in.

The only thing I kind of skimmed over because it wasn't highly relevant to the issue I had, was the CAS but from what I did read I'm not totally sure that could be the issue.

So check your ECU and let us know if you have any issues with certain gears like 5th/reverse or 1st gear.

I've adjusted mine without messing with the ECU? Still trying to figure out while I'm idling high and while the motor was running I rotated it and the idle did adjust accordingly. (just not the direction I wanted it to! Ha)

 

[whitesmoke]

No problems at all with shifting. When the rpms start to go up on there own and stays there, the car accelerates on it's own in every gear. It's like the rpms are stuck at that certain point.

My throttle cable becomes super tight when this happens and then it loosens up

Check my ecu how?

I tested the reaistance and each read 37. Do I need a new isc

 

[Gysgt Guy]

What are all the readings? From 1-2 2-3 4-5 5-6 and yes if you did accurately get 37 ohms then the motor does need to be replaced.

As for your throttle cable...if it's too tight, it not allowing the tb to close all the way. Try loosening it up just a hair and see what the results are.

 

[whitesmoke]

1-2 2-3 4-5 read 37 ohms 5-6 read 38 ohms. So I need to replace the motor?

 

[snowborder714]

That seems too low for my liking, assuming it's a black ISC. But I don't know what the acceptable range for a black one is.

 

[Gysgt Guy]

That seems too low for my liking, assuming it's a black ISC. But I don't know what the acceptable range for a black one is.

I'm not sure if the color matters honestly? I just replaced mine with a new black one and the ohms were the still in the range of 27-33.

According to the troubleshooting steps, if you are reading 38 that's one of the problems...oreillys auto parts have new ones with a 1 yr warranty for 90 bucks. Thats where I got mine.

 

[whitesmoke]

So it should read 27-33 ohms??

And I'm reading 37 ohms so I should get a new one ?

 

[snowborder714]

I'm not sure if the color matters honestly? I just replaced mine with a new black one and the ohms were the still in the range of 27-33.

If you got a black OEM ISC and it's reading in that range, then it's bad. The tan ones have that range, with the blacks reading 38-40 ohms.

So it should read 27-33 ohms??

And I'm reading 37 ohms so I should get a new one ?

Which do you have - black or tan? If black, it seems like it should be fine (I don't remember how low any of my black ones read). If it's tan, then you have an issue.

 

[Gysgt Guy]

Yes...before you go spend the money tho...## sure you read the meter right? I've been guilty of having it on the wrong resistance before and getting wrong results! Lol

 

[whitesmoke]

It's a black oem one.

 

[wpla]

couldnt it be the fast idle air valve? Before i put the blockoff plate on mine the rpms used to climb up to 3,000 when the engine was cold. idk if there is a way for it to mess up and cause the rpms to increase at random moments?

 

[snowborder714]

My guess is it's fine then. I don't know how low I've seen them read, but with the range that the tan one has, I would guess 37 is in range for a black one.

 

[whitesmoke]

How can I check if it's the fast idle air valve. And I thought the suggested range was 27-33. Or am I wrong?

 

[wpla]

im not sure how you could test to see if it is the fiav. i know that it is under the throttlebody and has two coolant lines running to it. It allows for extra air to go to the intake while is starting up cold, it works like a thermostat and as the coolant running to one side heats up it starts to shut the passage. i was thinking that the valve could be stuck open, but then you would probably get constat high rpms. sorry im not much help, im a little new to this. maybe someone else could have more input on this.

 

[snowborder714]

OP, read a couple posts above your last to see the range differences for black and tan ISCs.