What are the symptoms of having a bad IAC other than rough idle. I have an idle dip when the clutch is engaged but it is fine once it catches itself or I tap the gas. Could that be the issue or does that sound like a bad fuel pump

 

if you search IAC you'll find a lot of great threads on them i just changed mine if u need a new one amazon sells them for $190

 

check this thread u might find some useful info.
https://www.evolutionm.net/forums/ev...ge-my-isc.html

 

If you are having to tap the pedal to correct it your throttle may be sticking. Spray some WD-40 along your throttle shaft and see if that helps. If it does, then you need to replace your throttle body seals.

 

A bad IAC will fail to hold proper idle but it won't make the engine run rough. The IAC is just another throttle - a throttle that is controlled by the ECU.

 

Have the same problem on my 03. I've been thinking its the iac also. Checking it tomorrow to see if it's still in working condition . If the "grooves" or " teeth" are worn then I'm gunna replace it and see if that fixes the problem. If it does I'll make sure to let you know

 

Mine goes to 2k for a couple secs and trickles down to 1000-1100 and idles there and then randomly at a light sitting there it drops to 300 and pops back to abt 1000 and wideband gauge shows 11.0 or lower very rich and most of the time it's fine until those random idle dips comes around

 

it runs smooth if i get into boost and run it all the way to redline but only when the rpms drop back to idle..

 

alright, post back on here because if thats what it is i'll change it but if not i dont see the need in spending $200 if that will not fix it

 

It could be multiple things. Whats done to the car? Have you tried to do a boot leak test? If you have any type of leak that could cause a poor idle also. Do you have a vent to atmosphere bov?

 

heres the list: S2 cams w/ springs and retainers, walbro 255, 1450cc FIC, megan headers.. yeah i know they suck they were on the car before i bought it but the stock exhaust manifold is about to go back on. aem short ram, turbo xs intercooler + piping, head studs ebay 3 inch turbo back, & i am running the corn E85. It still has stock turbo and stock ECU. Im about to buy a tactrix cable so i can log it.

 

Have u set the biss properly?

 

oh and yes i do have a vta hks but its about to get swapped with a tial q

 

no. i just looked at another thread to find out what it is but still dont know 100% about the biss

 

Also have a hks that was vta , I recirc'd it ran a lot smoother but still had the idle drop. I've checked for a boost leak and didn't hear anything so I'm In a weird way hoping my iac is screwy so I can fix the problem