Increasing Idle during Driving. Someone help Please

[Generation1JeY]

Alright, in the morning or afternoon or at night regardless of temperature if i start my car up my idle is perfect, give it a minute and it will stay right around 800. But if i take it driving, at every stop i make whether it be a stop sign or street light or whatever my idle slowly starts to get higher and higher. Its the weirdest thing. After about 5 minutes of driving my idle is around 1000rpm, after about 15 minutes of driving my idle is around 1200rpm, and so on until it gets to 2000rpm. Once it gets to 2000 no matter how much longer i drive my car it will stay there.

Now if i park my car and let it sit for a little bit like an hour or so and come and drive it the idle will be fine again, but will start to increase.

I guess its just an engine temperature thing, as the motor heats up more and more its somehow affecting my idle, but i have no idea what i can do to fix it. It never surges at all its always steady, but its just always at a different rpm. i can't adjust it because SOMETIMES aka the first five minutes or so of driving the idle is fine.

Does anybody have any idea what i should look for with this? could it be my isc? FIAV? I'm so clueless.

 

[staticbrainwash]

Start easy and leak test. It almost sounds like there's a vac leak that increases when the engine heats (which is weird).

 

[tom04841]

It sounds like your idle air valve isn't functioning properly. it will cause weird idle problems, and does change with engine temp via the ecu. Check it out

 

[Gary 420A RS]

http://www.geocities.com/motorcity/downs/7678/dsmtests.html

 

[blackGSX2g]

When the car is fully warmed up and idling at 2000 RPM, check to see if your throttle cable is getting tight. When I first bought my car it did that, turns out as the throttle cable heated up it got tight enough to keep the throttle open enough to increase the idle.

 

[pneumo]

I have a feeling it's your throttle cable. It's too tight. The cable housing expands more when the engine bay heats up, and the inner cable gets tighter. Check it when it's cold, then check it after the engine is good and warm. I'll bet it gets tighter when hot.

 

[Generation1JeY]

Thanks for the input guys, i'll check the cable tomorrow and see if there's anything fishy with that, i will also try and do a boost leak test asap

 

[Kevin Jewer]

I've posted recently the correct way to set the throttle cable adjustment, some creative searching with my username should turn it up.

Edit> Here it is.

 

[ikickuintheball]

Definitely sounds like a big vacuum leak. I remember when I put my clutch in a couple years ago and I forgot to hook up the lines on the stock intake pipe. Just check all of your vacuum lines. It's an easy fix if it's that. Good luck.

 

[Kevin Jewer]

A vac leak would most likely cause a high idle all the time, not just after the motor warms up.

 

[ikickuintheball]

Mine definitely did that. I had no clue what was going on. I figured it out the next day when I saw I didn't hook up the hoses on my intake pipe. The idle went from 1k one light then to 1.5k the next up to like 2.5k by the time I got home after a half hour.

 

[Generation1JeY]

Alright guys i finally had some time to play around with it and it did turn out to be the throttle cable. it was so weird like i checked the tension when it was cold and when it was hot and it seemed the same, but i noticed that i tightened the throttle cable mounting plate down so that it had a little bit more tension. I could tell by the discoloration of the slots you could see where the bolts were initially and when i recently took my motor apart i reinstalled it and tigthened it so there was a little bit more tension. So while the motor was hot and idling high i killed the motor, disconnected the throttle cable from the throttle plate and started her back up and the idle was perfectly fine again. I guess an easier way would have been to just loosen the bolts and the mounting bracket would have just pulled itself to the right place and then retighten it, but i just wanted to make sure haha i'm weird.

Anyways thanks for the help guys i have perfect idle again