Help plz idle surges
 

Hi all, i just got a 98 rs last week (i think rs stands for really slow) any way I'm having the same problem as this guy https://mitsubishiforum.com/m_180744/tm.htm for those to lazy or cant be bothered with clicking that link basically my idle is surging between 300 and 2000 rpm's while idling but the car drives fine. Any way i came across this link (plz click this one) http://www.autocomputersupply.com/in...ustom&ID=8 does any one think this could be our problem? They have them at advance auto parts for like 70 bucks. Or should I grab one from a junk yard just to see it it helps?

RE: Help plz idle surges
 

most likely its either your ISC or your EGR valve. Do you have a check engine light

RE: Help plz idle surges
 

I had this same issue but on a GST and replaced that along with adjustment of BISS Base Idle Set Screw. and it worked fine after that. One thing i would suggest before just buying the part is check for vac leaks.

RE: Help plz idle surges
 

its the EGR. my buddies 98 talon had this issue.

RE: Help plz idle surges
 

It can be the egr but i replaced that as well there is a total of 5-6 things that can do this so testing is recommended why buy parts to find out it is a vac leak.

RE: Help plz idle surges
 

i have a vacuum leak to. were was urs at?

RE: Help plz idle surges
 

OK here is what i have done so far. Checked for vac leaks none as far as i can tell. Ordered a ISC, installed it and when i did the motor would idle at 4000 rpm's. It never went down! My friend used a stethoscope to listen to the ISC and said it never stopped running when it should of and was stuck at wide open which is why the car was turning 4 grand as an idle. So i took out the new one cleaned the old one and put it back in. Then the car did the exact opposite it bogged down and died every time I let off the gas. I had to cut a cap off of a screw that could adjust the idle manually and kicked up the idle just so the car would run. At this point the car was running like **** on my way to take the ISC back. While i was there i got some throttle body cleaner and used it and an old tooth brush to clean my throttle body. After a hell of a time trying to get her to start she finally did and now the idle was to high it was at about 2 grand. So i ended up putting the idle adjust screw back to were it originally was. Now I'm right back to were i started :(

The CEL never has came on exept for when i first turn on the car, but all the dash lights do to for a couple seconds. What is a EGR valve and where is it at. And does any one know a good way to look for vac leaks i just tried listening and feeling for the leak i dunno what else to do. Thanks

RE: Help plz idle surges
 

On the last attempt did you put the new isc that you got after you returned the broken on in? also did you check the O-ring where the isc was? was it damaged at all? reason i asked is because a lot of people just throw the isc in and don't look at the o-ring and it leaks like crazy if it is damaged or missing. also to check for vac leaks best way to do it is get a can of starting fluid and spray a little at all the joints where vac lines or TB gaskets are when u spray each line listen and the idle will jump then go back down it will only do this for a few sec when u spray the line. The EGR is located right below the TB has 2 screws in it looks almost like a thermostat housing oh and it sucks to take off but if you do get it off look in it and see if there is an excessive carbon build up you can clean it see if it holds pressure should have 2 vac lines on it. or you can just go buy a new on on my car i had to install the isc "replaced the o-ring" and then adjust the biss.

sorry missed this EGR Exhaust Gas Recirculation

Edit: Your egr is differant then min looks and all here is what it looks like
http://www.partsamerica.com/product_...e/fe3075-1.jpg
Img is from checker

RE: Help plz idle surges
 

No i havent installed the new, new ISC yet I'm going to tomarrow i ran out of sunlight to work in. And i tried my best not to break or damage the new O ring while installing and the old O ring seemed to be in good order for being allmost ten years old and thanks for the tips with that and how to look for vac leaks.I hope its not theEGR valve thats more expencive and more of a pain. Allso seems like more ppl are pointing at the ISC than the EGR but like when I bought the ISC the sales person was like who told you yours was bad and said it could allso be the throttle positioning sensor. My first week with this car and i hope this turns into a learning experiance and not a nightmare. But thank you very much for yours and every ones help i do apreciate it ill keep updateing my progress till its fixed and post the fix [rant] I hate it when ppl ask for help fixing there car and when they do fix it they dont post what they did to fixit, makes it harder to find fixes that actually work on here [/rant]

RE: Help plz idle surges
 

Ok cleaning the throttle body helped alot. It took a while to adjust the BISS right but the problem seems managable. It only does it every once in a great while now and it doesnt fluctuate as much. So im just going to live with it for now. Thanks for every ones help!


p.s. this is the most hands on car ive ever had.