[RESOLVED] Idle surge, then CEL?

[JMiller]

After i drive my car for about 5 min the idle raises to 1100rpm but i can get it to drop to 900 by tapping the throttle. Well today sitting at a light my idle jumped to 1500 and my CEL came on. I wish i could find out the code but my obd port wont connect to any scan tool. Also i have a fiav/isc block off plate on my TB so i know its not related to that. Could my TPS be causing this or maybe a bad o2 sensor? Any help would be great, thanks.

 

[GSX93DSM]

I would check you tps. That sounds like typical tps syndrome. Also take a look your fiacv. That could be a problem as well.

DSM simple test page

 

[JMiller]

I was thinking it might be tps related also. And it can't be FIAV cause i dont have one. I'll set my TPS later if it doesn't rain.
Thanks

 

[97gstnick]

I had a similar problem like this and it was due to my throttle sticking a little. A good way to find out is to pop your hood and with motor running with its high idle, pull your throttle closed real hard. If idle goes back to normal then it probably is your throttle. Also check that none of your vacuum lines are cracked/leaking. Do a boost leak test with soapy water.

 

[JMiller]

how would i fix my throttle sticking open some if i have to FORCE it closed, what can i do to make it close the way its supposed to. And once again it seems to do this only when the car is at operating temp.

 

[95blackGsTurbo]

Your best bet is going to be to remove the throttle body and give it a good cleaning. Odds are you just have a buildup around the shaft or plate and it's causing it to not close all the way.

 

[JMiller]

when i put the block off plate on i cleaned it until it was spotless and i checked to make sure it was closing and opening properly. But when i put it back on the car this problem occurred so i removed it again and took the throttle plate out and cleaned it some more and I was 99% sure it was opening and closing the right way.

 

[95blackGsTurbo]

Then you probably messed up the TPS when you cleaned it out or didn't index it properly.
TPS Adjustment

 

[GSX93DSM]

You didn't tear the throttlebody apart and pull out the throttle plate.

 

[JMiller]

Yes i did remove the throttle plate, both times. But i didn't really clean it the first time i just wiped it off and put it back. About my TPS i now have a Multimeter and will set it as soon as weather gets better.

 

[97gstnick]

When you removed the throttle plate and reinstalled it you probably had it misaligned just a hair. And that can be enough for it to rub on the inside of the throttle body and keep it from closing fully. Look for scraping on the inside. If indeed this is the problem, you can either readjust the plate or file it down just a little. Another option is to tighten your throttle spring one more turn.

If none if this fixes it, I highly suggest a boost leak. You might have a pinhole leak, and that is enough to raise your idle.

 

[JMiller]

Yeah, i just set up my TPS the correct way(vfaq way) and its still doing, an i realized if i slowly let off the gas it will only drop to about 1200 but if i tap real quick it drop to 500 then raises to 850-900 which is were i have it set. Tomorrow i will pull the TB and mess with the plate and probably give the spring another turn. I was actually thinking about turning the spring one more turn the last time i had the TB off but i thought it would cause my pedal pressure to stiff.

 

[97gstnick]

Yeah, i just set up my TPS the correct way(vfaq way) and its still doing, an i realized if i slowly let off the gas it will only drop to about 1200 but if i tap real quick it drop to 500 then raises to 850-900 which is were i have it set.

This is the exact same symptoms I had when my throttle was sticking. And do a boost leak test!!

 

[JMiller]

Fix Throttle body, and do a BLT. Check!

 

[JMiller]

Ok, i took the TB off today and filed down the throttle plate some and cleaned everything. I tried to turn the spring one more turn but couldn't, so i put everything back together and adjusted the BISS to compensate for the extra air coming in. And it still gets stuck when i slowly release the throttle. I also noticed that it doesn't get stuck when the car is off, but when its on it will stick. Any ideas.

 

[Squirrel8811]

Vac test. If it were me i would find out what is stopping the car from hooking up to a scanner, fix that, then read the code to point you in the right direction. It could be any number of things and something like this will drive you mad trying to find it by testing/replacing everything.

I work at autozone (which doesnt make me a pro but ive been at school for this for 3 years) and it stumps me everyday that someone will just throw parts at in instead of DIAGNOSING the problem and fixing it. Its really funny when they throw hundreds of dollars at it and its their gas cap or something stupid.

 

[97gstnick]

Ok, i took the TB off today and filed down the throttle plate some and cleaned everything. I tried to turn the spring one more turn but couldn't, so i put everything back together and adjusted the BISS to compensate for the extra air coming in. And it still gets stuck when i slowly release the throttle. I also noticed that it doesn't get stuck when the car is off, but when its on it will stick. Any ideas.

Did you do the boost leak test? Use soapy water, trust me on this. Spray your whole throttle body with it and pressurize the system.

 

[JMiller]

I got it fixed, i took the TB off AGAIN and took it apart and turn that spring a few times then put it all back together and its working fine now. Thanks everyone(mainly 97gstnick) for all the help.