There is a vacuum line on the BACK (against the firewall) of the intake manifold that is hard to see and easily comes off. Zip tie it back on if it came off.

Also go over all the vacuum lines, the heat from our engines likes to dry and crack vacuum lines.

 

thanks migs647, i'll check it out

 

nope, looks good, i don't think it's a vacuum leak

 

get a can or starter fluid and spray all your connections as the car is running if the idle jumps up when you spray a spot you found it. its not the best method but it can help in a pinch sometimes. check the larger vaccum line under the intake manifold on the egr valve....that one has been prone to blowing off

 

It was suggested earlier in the thread by mplspilot.

One thing you can do, that takes about 3 minutes and can save you a ton of headache if it is the issue...as I found out the hard way.

Take off your upper intercooler pipe at the throttle body. You will see a small black plastic bulge under the throttle body inlet. This is the housing of the ISC. It stands for Idle Speed Control. It is held to the throttle body by 3 screws arranged in a triangular pattern. Unplug the ISC motor(plug is on the housing). Carefully remove all 3 screws and remove the ISC motor from the car. Looking down into the ISC motor that is now in your hand, you should notice 3 tabs around the edge of the inside. They sit in 3 grooves in the outer housing. If they are worn down at all and the ISC motor can spin freely inside the housing, then it cannot control the idle. The tabs, and the outer housing are plastic...and plastic wears out. If it is worn out, get a replacement and that should fix things.

I personally experienced a bad idle when I bought my car that the prior owner had never remedied. Turned out the ISC was long since worn out.

*EDIT* I also notice you have an 03. If you have a higher mileage car, this can definitely be the issue.

Also, as stated, make sure you don't have a vacuum or boost source open anwhere.

Happy hunting.

 

great post, this is the issue, i'm currently hunting down a new Idle Air Control Valve, the unit is over $300 at the dealer. Do you know offhand if the one off my 2003 Evo VIII is interchangeable with one from a 2005 Evo 9? For the record, my 2003 Evo VIII has 103,000 miles. Thanks GotWheelHop!

 

Don't ever spray starter fluid on a running engine. If surface temps are high enough, such as the exhaust manifold, then a flash fire can be started. Instead, use Mass Air sensor cleaner or Throttle Body cleaner commonly available at any auto parts store.

Also just FYI the one that I told you about is off of an 06 IX but I used it on my 05 VIII for a period of time.

Josh

 

LoL valid point...Just try to help someone out who sounded like they didn't have the equipment for a true boost leak test

 

Let me know if that work...I'm having the same problem.

 

Anytime, man. The IACV is universal between 03-06 so you should be able to source one. Glad I could be of help, as I know troubleshooting the idle can be a bugger.

 

you know, you should really just take the time to go make a boost leak tester... a few bucks spent will save you a **** ton of headaches, and you will always have it.. i really think youre looking at the problem, and not seeing it... check your hose clamps from top to bottom

 

Check your tps, that might not be pluged in all the way, I had this problem about a weeek ago.

 

Just let the car sit and idle for a few mins before going out and driving... It has to "relearn" so-to-speak

 

Reviving an old thread here.

Question: Should any part of the ISC move freely by hand ?

I ask because mine does not move at all.

Paul

 

This is the worst advise ever. DO NOT touch that screw, The idle is controlled by the IAC or idle air control valve. This screw is merely there to stop the throttle plate from closing entirely. If it were to close the enitre way it would stick anytime you let completely off the gas.