Rough uneven idle

[Manboy4870]

Hi guys pretty new to mitsubishis, however I got a very annoying problem, I have a 94 gsr cc with a 4g93t in it, it's been idling quite rough an uneven only fluctuating a couple of hundred rpm, from between 800 and 1k sounds kinda like a miss, it's got new plugs and leads and I've put a whole new throttle body on it and nothing has changed, the vac gauge is sitting on neg 16 and it drives ok the miss is only a little noticeable at higher rpm, and seems the power is at a loss a bit, the stepper motor seems fine as when I put the ac on it jumps up accordingly, it happened by itself , also sounds like a hard start like a low battery but that's new too. Any ideas????
Thanks chris

 

[GSR94T]

Idle Speed Control valve are a common fault on these. Try a known good one if someone has a spare one you can maybe borrow on here, then if that fixes it, buy another one
These are a main cause for Idle to jump all over the place, and sometimes can freak out even more when air con is turned on - that was my problem when I had a GSR with the 1.8 in it

Also are you running an external venting blow off valve? If so put on a plumb back back onto it - these cars a very sensitive ive found. I used to get idle issues and stalling with an external venting BOV

 

[Manboy4870]

Makes sense I was leaning towards the iacv but they are pretty expensive, yeah it is atmo but the bov is as tight as possible so it just flutters

 

[khubner1]

magnas use the same unit if your willing to take a multimeter with you to a wrecker to test them before buying them

 

[4piknup]

There is a sticky in the evo 1-3 section that has utube links to test your isc.

 

[BMGTZ]

check that the base idle setting screw isnt too far out as that will cause the engine to hunt...miss and generally be a shit

 

[4piknup]

Google 'biss setting vfaq' to get you close to right

 

[clone]

chris4810 , let me know how you go , im in townsville also and have the same problem. Havent got around to checking my resistanc in my ics but i shall attempt when i get time at work . (i dont run a bov so i can eliminate that problem)

 

[Manboy4870]

No worries thanks fellas shall let you know hopefully I can find one today

 

[Manboy4870]

So the magna ones are the same? looks the same but are they the same length when they adjust?

 

[4piknup]

If they screw in and plug is the same, they are the same.
I thought there was some difference? I have 3 throttle bodies here, 1 is 2.0l sonata, tr v6 magna and Gsr 4g93t.
I think that I couldn't put the magna or sonata isc in the 93t throttle body.
The v6 magna tb goes on, but tps clashes with vacuum take off on plenum.
The 2.0 sonata one is what I using now. The isc interchanges between v6 magna and the sonata, have alook and make sure they attach the same

 

[EVOCPE]

Make sure it turns the same direction to the 4G93T TPS

 

[Manboy4870]

Well the iac fits off the magna ran a bit better but still hunting in the idle so I reset the ecu ran horrible after that so might have to drive it and reset the tps coz I haven't done that since I replaced the throttle body :$

 

[khubner1]

also adjust the tps it should read 0.6mv at throttle closed

 

[Manboy4870]

Does it have to read at 4.5 at full open ?

 

[EVOCPE]

http://www.plymouthlaser.com/tps.htm

http://www.oocities.org/motorcity/downs/7678/dsmtests.html

 

[Manboy4870]

Well I did everything I can an its still not perfect, must be time to take it to Mitsubishi , however would anybody know why it idles perfect when the ac is on, and at 110 when its not on lol wtf

 

[khubner1]

Get some contact cleaner and hit the afm with it then put some carby cleaner through the tb

 

[milkandoj]

Have u also checked the throttle closed switch? It tells the ecu when the throttle is closed and it should be in idle, if its stuffed it will hunt, happened on my car.
Its the switch you screw in and out that adjusts the throttle opening at idle, that switch must be working.

Im pretty sure this is logged separately to the tps signal, jeez the cars been parked up for 6 months I've forgotten!

 

[oggy]

i've currently got idle problems with mine too atm, bitch to sought out - so many things to check and adjust to try get it back in order lol! mine still isn't right :lol:
1 thing that caught my eye though, you said your vac at idle is -16 on your gauge.... unless your car has got cams, it should be pulling -20 ish at idle. you might have a vac leak somewhere that is causing some grief. It would be worth checking, if only to eliminate it from the list