My car right now is idling at 4700RPM. When driving without even hitting the gas it gains speed all the way up to 5000RPM, at this point if you hit the brake sometimes it well slow down losing RPM until 3000RPM which at that point it kicks back on to 5000RPM. First: I checked the throttle to make sure there was no sticking and that it was in its correct postion. Also tryed to reset my computer. Still continues with problem. Second: I replaced the Throttle Placement Sensor. Still the problem continues. Third: I made some phone calls and was suggested that I replace my MAP sensor or "some airflow sensor". I called the Mitsubishi dealer and had a talk with the garage there and they said it might be the computer. I was going to get it put on a tester, yet thats going to be around 100 dollars for itself. Any suggestions or simular problems please respond.


Also: There were no check lights on. I checked for error code anyways and it was ok. Also checked the vacumm lines as best as I could... Usualy you can hear a hiss from a leak, but not at 4700RPM

The Car is a 1996 Eclipse GS 5-speed

Did you pressure wash your engine bay like the last guy who had a post like this did?

you could also have a leak (such as a vacuum leak) after the TB.

Well I did pressure wash my engine bay. Its been a good two weeks since. Let me know what to check. Thank you

I would reccomend checking that your throttle plate is closing all the way at idle. The washing may have some how caused it to stick. Pull off the intake to check. Just be careful and not have people standing around throwing screws in the vicinity of your exposed throttle body. ;)

Negative on the throttle sticking during idle. It seems to be ok.

You may also want to take a look at your IAC (idle air control) valve. Could be opened, that would explain the funky idle.

Can you explain where this valve is. Im pretty sure I know where this Valve is. I think its below the TP (Throttle Positioning) Sensor. If you could give me advise on what it should look like and what postion it should be in...basically how to test to make sure its working.

a BIG vac leak will do that. Try checking your PCV valve, the vac hhose that connects it on both sides... if it slips off, that will definately happen... cause it happened to me...

Just checked PCV Valve and hoses to and from and they apree to be on and no leaks.

Most likely your IAC..idle air control valve..yep, its right under the TPS...its either that, or a big vac leak, but you would def hear that hiss from a vac line if it was...check your vac line that goes to the power brake booster too...Its the large vac line on top of the intake mani...

check all the vacc lines runnin to the rear side of the intake mani...

there is a three prong deal on the pass side, a sensor in the middle, and your brake booster deal on the dr. side...

also, did u throw any codes??? autozone will hook u up w/a datalog for free.. if you are 95-97, u can do the key dance... look on the main page for info on that...

p\good luck

I just went and ordered a new IAC. It should be in tuesday. until then please keep the suggestion coming....Thanks for all your help so far.

I think its the IAC as well.

Here's a little story for ya. I had this problem with funky idle, and actually got a code about the IAC. So I took it off, jacked it in and out a bit, put it back on and it worked again AND the code was gone. That was like 4 years ago and I still have no problems with it.

You might want to give it a shot. It may or may not fix the problem alltogether. You're getting a new one on Tuesday anyway. If the IAC motor is still not responding, you JUST MIGHT be able to tune the idle down a bit. Pull it out for a lower idle, push it in for a higher idle - that's all the computer is doing.

The only other thing I can say is that from what I remember it was a bit of a biotch to get on/off with the TB installed, but it can be done.


ride__________95 Eclipse RS : 5 speed
power________Gude cams : AFX UDP : ram air : test pipe : Thrush glasspack
suspention___BOMZ F/R upper strut bars : ES inserts
shizzle_______AutoCommand remote start : Dual air horns : Kenwood KDC 5000 : Rampage sub
incomming___lower strut bars

another thing that i've seen that could also be a problem i getting on of the wires either wet or burnt right by the harness, usually when the IAC gets wet this happens also, check if the wires aren't like cut or burnt which the water could've like shorted out.

My guess is that the IAC is carboned up, and the valve inside there is sticking...it happens more than you might think..try to take it off, clean it with some carb cleaner, and put it back in..you got nothing to loose since your gettin a new one anyway..

stupid question...wheres the PCV valve? does it go bad? Thanks

I pulled the IAC out and seen if it was jammed in, it wasn't. It was all the way out in the position it should be in for lower idle. Put the IAC back in and its still idling at 4700RPM. I hope this doesn't mean that my IAC is fine and its actually another problem and I just waisted 52 dollars from ording a new one.

JZA69- The PCV Valve location: There will be a tube coming out of the front of your throttle body to a plastic piece (PCV Valve)then it makes a 90 degree turn and heads into your valve cover. That should be what you need to know to find it. Also: they do go bad.

To check if its ok or not. you'll have to remove the tube from the PCV valve. Theres two tubes connected to oppisite ends. The one you need to remove, is the one going from the PCV valve to the Valve cover. look into the pcv valve and you'll see a silver little circle, this is connected to a plunger device. Just take a nail or something thin and push it in and out. If it is jammed up in it and wont move then its bad. If it plundges in and out its fine.

Thanks for your help man...Goodluck diagnosing your messed up idle.