High Idle Troubles

[98cobracool88]

hey there fellow mustung guys..

i recently purchased a 98 mustang cobra as my first sports cars ive been into crotchrockets... Anyways.....

when i pull up to a stop and take it out of first it wants to idle at 1,200-1,400rpm for about 5 seconds before dropping to 900rpm. at one point it was idling at 1,800-2,000rpm. i would tap the throttle and it would go down.

it will also jump up and down from 900-1,150rpm randomly when it is not sticking at a high idle.

it is flashing 2 codes:
P0114
P1443

ive cleaned my throttle bodies, replaced the idle check air valve and cleaned the egr valve, along with traced all lines and there is no air leak that i have found. the throttle cable is not sticking.

guy at autozone said the sensor on the side of the throttle body needed to be adjusted but not sure. sometimes those guys are full of shit but i dont know.

im no professional mechanic but know enough to get by. i mean i went to school for motorcycle mechanics but completely new to the auto mechanics

if anyone can throw some ideas at me...please im all ears and always looking to learn something new or if you have any pointers at stuff to watch out for.

thanks.....josh

 

[HandsomeRob]

Adjusting the TPS sensor is a must if you haven't done it in awhile.

 

[Beerdog80]

Google is your friend. VERY common problem with SN95's. Tons of write ups out there.

 

[mwolson]

Don't adjust the TB unless you know what you are doing and have the ability to datalog. If you must adjust it, adjust it until your ISC duty cycle is about 30-35%. You should never have to adjust it unless a PO has screwed it up, or it is a crappy aftermarket TB.

Use a smoke test to confirm no vacuum leak. If you don't have access to a smoke machine, here is a great cheap way to do it: https://www.youtube.com/watch?v=zMok2y05jNE

Unless you have a simple issue such as a vacuum leak or a stuck IACV, you need to datalog to see what is going on in there. The PCM uses the IACV to do coarse control of idle, but it uses spark for fine control. Without data you are shooting in the dark trying to fix idle issues.

 

[chrisconsin]

Use a smoke test to confirm no vacuum leak. If you don't have access to a smoke machine, here is a great cheap way to do it: https://www.youtube.com/watch?v=zMok2y05jNE

100 cool points, that was awesome!

 

[98cobracool88]

so i watched the video and did what the guy said and had smoke comin out of the flange on my idle check air valve, which i just replaced last week. is that suppose to happen?

 

[mwolson]

Nope. That's a leak.